Even for me, who has gotten used to 6500k lights, higher temps remind me of old hospitals. Not just led, even cheap fluorescent tubes that come with battery lanterns are also offenders.

@RRK:
That was one of the worst things that could happen to me, I suffer from night blindness, and the high colour temperature means I struggle to see clearly. 
Under sodium lighting, particularly LPS, I have no problems at all.!

Another pet peeve I have about lighting is the amount of dead lamps when multiple are present (not only leds). A poorly maintained office building where the rooms are good but the hallway lights are half dead, or flickering. Led was supposed to solve this problem but since making a high voltage low amp power supply and putting the leds in series is easier than making a low voltage high amp power supply and putting the leds in parallel.

This may be a little irrelevant but it further enforces on the problem where the best working lamp breaks while the eol/bad condition one is fine. When I was extracting two VFDs, the one with small pins and chipped glass survived but the best condition one with long pins lost vacuum (black spot=vacuum good & white spot=vacuum loss).

Another pet peeve that has really been bothering me is that I often get frustrated whenever I encounter collectors who give contradicting advice when it comes to lamp/ballast combinations in which a European collector might claim that the setup is “compatible” and “safe” while a North American collector would claim that the same lighting setup is “incompatible” and “dangerous”. Has anybody else ever dealt with a similar situation like I have been facing?

The most important thing to avoid such things is to make your question as good as possible. This means for lighting devices that you should include a datasheet with current and voltage, specify your mains voltage and frequency etc.

For ballasts, this is not always easy to find. They're also often designed to be 'user friendly' which means that the current/voltage is not always specified, only 'X watts'. When the input from the manufacturer is vague, the output from people who are trying to help will also be vague. Garbage in, garbage out. Vossloh Schwabe often prints the different compatible lamps including their running currents on the ballasts, which is awesome, but that's far from universal.

There are also different types of ballast. Over here, the most common one is a simple coil in series with the tube. Leakage transformers are very rare here. So that kind of stuff you also have to take into account to specify. 

If everything is quite vague, it will take some discussing and potentially conflicting opinions before you get to a workable solution. That's the reality of online collaboration between different people. I've seen on many occasions people getting angry and moan at the people who are voluntarily trying to help them with electronics engineering and repair related questions and are discussing amongst themselves to figure out what's right. And to those i can only say:

Go find an engineering/consultancy firm, and specify that you only want one single answer and one answer only - even if that means that you might miss some important nuance.

when a fixture housing can physically fit larger lamp and gear, but a lower wattage setup is installed

Replacing quality vintage fixtures with integrated LED rubbish, designing modern decorative fixtures with integrated LED instead of replaceable lamps, and also retrofitting quality fixtures with LED only to replace them late with LED fixtures!

Sometimes, they also replace older good quality leds with a cheap new leds. Compare early led bulbs with metal heatsinks to plastic ones now.