@Medved, I have absolutely no idea... but you may be onto something... I'll check to see if it does it again while
I'm driving. It's definitely on occasion, and it's very dim so it's not very noticeable while I'm driving.
I only notice it through reflections of the car, like from a window of a building.
It does happen during the day, although my car does NOT have daytime running lights. Lights on my car automatically
shut off during the day. This was also the case with my old Pontiac Grand Prix.

@Medved, I have absolutely no idea... but you may be onto something... I'll check to see if it does it again while
I'm driving. It's definitely on occasion, and it's very dim so it's not very noticeable while I'm driving.
I only notice it through reflections of the car, like from a window of a building.
It does happen during the day, although my car does NOT have daytime running lights. Lights on my car automatically
shut off during the day. This was also the case with my old Pontiac Grand Prix.

Find some helper, one of you sit in the car, start it (you may first try without starting, just turn thr ignition on, but it is quite possible it will work only if really started), turn off all features like auto hold or so, shift drive and then turn the wheels left and right. If it is the corner function, the lights would turn ON visibly slowly and stay on for some seconds after you straighten the wheels back, then again turn gradually off. The turn on and off is really artificially made very slow, something like dome light fade out when you close the door or so.

But according to what I understand from this post , the G6 has DRL, they just turn ON not with the ignition (as it is common with most cars today), but after you shift to Drive. But then I would expect both sides to light up...

And this picture makes an impression to me there is a small bulb just on the inner corner of the headlamp assembly, at position where I would expect the "corner" lamp to be (to shine in the right-front direction). But it could just be a phantom reflection, so look to your car there...

@Medved, I'm not sure why those headlights on that particular Pontiac G6 look different. I'll have to look at my car
to see if there are any differences. As for the post, I can at least manually turn off and on my lights with a small switch
on the tip of the turning indicator switch. Seems like that person who posted that might be running into a different problem of some sort.

Daytime running lights are for safety purposes in cloudy or rainy conditions. They allow moving cars to be visible from further away.

In Europe, I believe it’s mandatory in most places to have running lights on your car. My VW Jetta has full time running lights. The low beam 55 watt filament is always burning when the car is in drive. The headlight bulbs seemed to burn out quickly due to that feature. My Subaru Legacy has full time running lights too, but they burn at about 25% power. I’m not sure what the rules of the road in Japan are regarding day running lights. 

I think day running lights are a smart feature, especially if you suddenly drive into rain or fog and forget to turn on the headlights. Motorcycles in my state are required to burn headlights at all times to enhance their visibility and safety among larger cars.

@CEB1993, yep both my older motorcycle and my newer motorcycle had daytime running lights. Seems like it
was a mandatory thing for Britain as well I'm guessing, since both of my bikes are British.
Here's what pisses me off a bit... my old bike had both lights running regardless of whether they were low
beam or high beam. My new bike has only one light for low beam, and then both lights for high beam with one
light being the brighter one. I don't get it. A lot of Honda's super sport bikes (Japanese) have the same one light
feature as well.

My Isuzu Trooper "project car" has "cornering lights".  White lights mounted at the front corners that turn on solid when that side turn signal is on.  In this case, they are the lower half of the corner wrap-around light, with the upper half being the amber turn signal/marker light.  When I hooked up my battery (jump starter) and tested the lighting, they didn't seem to work.  Either the bulbs or burned out, or being the basic S model, the feature isn't active on that model.

My snowmobile has an unusual light setup.  The headlight and tail light are on whenever the engine is running, being powered directly off of a lighting coil, and usually dim at idle (not stabilized by the battery), which is typical of snowmobiles.  The headlight unit, mounted in the center of the cowl under the windshield has 3 lights.  The center light is the low beam and the two outer lights are the high beams.

@Medved, I'm not sure why those headlights on that particular Pontiac G6 look different. I'll have to look at my car
to see if there are any differences. As for the post, I can at least manually turn off and on my lights with a small switch
on the tip of the turning indicator switch. Seems like that person who posted that might be running into a different problem of some sort.

Well, that post was mainly about the switch not working and lights stuck in Auto mode - so asking for help to fix the defect. But within the text it described how the thing is supposed to behave in that Auto mode with that car model, that is why I have linked it there.

I’m not sure what the rules of the road in Japan are regarding day running lights. 

That does not matted for your car even when made in Japan. These things are always adopted according to the rules in the country of sale, so regardless what Japaneese rules say, your Subaru behaves according to what rules in your country say. Unless it is some shady import, but I doubt that (such shady import would have the driver seat on the right side of the car to begin with,...)

@CEB1993, yep both my older motorcycle and my newer motorcycle had daytime running lights. Seems like it
was a mandatory thing for Britain as well I'm guessing, since both of my bikes are British.
Here's what pisses me off a bit... my old bike had both lights running regardless of whether they were low
beam or high beam. My new bike has only one light for low beam, and then both lights for high beam with one
light being the brighter one. I don't get it. A lot of Honda's super sport bikes (Japanese) have the same one light
feature as well.

That seems like an unusual feature. Maybe the optics are different for a motorcycle vs. a full sized car. It seems like motorcycles use halogen bulbs with two filaments (such as the 9003) to combine a low beam and high beam from the same fixture.

@CEB1993, I think that was the case with my old bike, but I'm not sure about the newer one.
Also, the newer one does have projectors. The old one didn't.

@Medved, I keep forgetting to check my car to see if it has the same headlights as the G6 that you
posted a link to. I'm gonna try to snap a picture of it here soon and upload a pic of it.

That seems like an unusual feature. Maybe the optics are different for a motorcycle vs. a full sized car. It seems like motorcycles use halogen bulbs with two filaments (such as the 9003) to combine a low beam and high beam from the same fixture.

The motorcycle beam is indeed very different from cars, it is mainly due to the different steering geometry - motos leaning into curves, vs cars staying in the same position vs ground surface.
The beam uses to be symmetrical and it differs, whether the headlight is mounted on the main body or the front fork assembly (so it turns with it).
Because moto is a  narrow vehicle, it suffices with just one headlight. The low beam is strictly regulated, with limited output, so just one reflector for that function is good enough. High beam allows way greater output, so many makers opted for double reflector high beam assemblies, to use the same bulb type everywhere (for the convenience to suffice with less spare lamps in the toolbox you have to carry).

@Medved, I keep forgetting to check my car to see if it has the same headlights as the G6 that you
posted a link to. I'm gonna try to snap a picture of it here soon and upload a pic of it.

Well, Im not even sure the headlight in that picture really had the separate cornering bulb, the photo is not detailed enough. But for sure many cars use to place the corner lamps exactly there - it suffices with the high beam reflector surface, so no need for extra space on the common reflector body.

And indeed, Im still curious how your car really works... :-)