Had a couple of electronic ballasts that went EOL passively, I think I salvaged the wiring and tossed the rest. As for magnetic ballasts, I had a couple that felt a bit sketchy when I ran it but nothing that really failed in a violent way.

I also got a couple of fixtures with failed ballasts that were dead before I got them, those I just tossed the blown ballast and put in a new one.

And finally I have a couple of used HID ballasts where the dry capacitor is losing capacitance. The cores are still good so I'll probably replace the capacitors if I put the ballasts in a fixture.

I had a visibly fried GE 100w HPS mag-reg ballast that I decided to try out for the heck of it and see what it would do, and it made a loud arcing noise with the lights in the house flickering and after about two seconds of it I unplugged it. The lamp never l had in it never lit up. It also welded the cord I had used to the terminal block. I never did see it arc either. The ballast was fried due to a bad capacitor, which had oil all over it, thankfully non-PCB.

 I've never had a ballast blow but I've seen a couple do it . I have had a capacitor release the magic  smoke inside my Norelco 180w SOX streetlight . Also , back in my teen years , I wired a 50w HPS ballast improperly causing the lamp to grenade into schrapnel all over my bed room !!  I wasn't allowed to mess with lights in my room after that one !

If I were you, I would stay away from Twitter and tik-tok since they are addictive media material

It is a good thing that I'm not in the facebook, twitter, and other media platforms there saving for this lighting gallery and Internet Movie Car Database sites.

Remember how random kids ask if your pphone has games at family reunions? Well i was a victm with my drawing tablet. Some kid cracked the front glass so bad, it made a hole where water slipped in and ruined the display. Lesson learned.
(sorry for spelling error, im typing on my pibook with a microscopic keyboard)

Nope. Only DX mercs and coated HPS lamps were clearbanded. C and W and coated MH lamps were cleartopped until the early 1980s or so. The N was fully coated in the late 1970s.

I also have a Sylvania MS400/C/HOR probe start metal halide lamp that is definitely a cleartopper in my collection.

After reading about some collectors attempting to run 700W H35 mercury vapor lamps on 1000W M47 probe start metal halide CWA ballasts by derating the series capacitor value from 24 microfarads down to 18.5 microfarads with relatively good results, I am interested in trying to find an appropriate capacitor value that is appropriate for running the rare 425W H40-17 mercury vapor lamps on 1000W M47 probe start metal halide CWA ballasts.

For reference, the 425W H40-17 mercury vapor lamps have an arc voltage drop of about 265V and an operating current of about 1.7A and is NOT interchangeable with 400W H33 mercury vapor lamps; the 700W H35 mercury vapor lamps have an arc voltage drop of 265V and an operating current of 2.8A; and lastly, the 1000W H36 mercury vapor lamps and 1000W M47 probe start metal halide lamps have an arc voltage drop of 265V and an operating current of 4.0A. So far, my initial guess is a capacitor value somewhere around 10 to 12 microfarads for the 425W H40-17 lamp if I am not mistaken. I am interested in answering this question because I am looking for easy ways to help collectors safely run 425W H40-17 mercury vapor lamps just in case they find any in the future, but they are extremely hard to find as they appear to have only been produced during the 1960s and would like them to make sure that those lamps would run properly.

The source that I used to find the electrical characteristics of the 425W H40-17 mercury vapor lamps can be found on the link below on page 15 of the following document:

https://www.scribd.com/document/394833080/Westinghouse-Mercury-Lamp-Brochure-1961

I've noticed it is quite random. Sometimes, there is lots, and sometimes there is none. I have lamps that flash a lot and some that almost never flash. Sometimes the flashes are long and intense, other times they are brief and not too bright. I've even had some flash after running for a few hours (although less intense).

When I was in high school, the 400W halides in the gym would each flash once. They would warm up to the clear mercury phase, stay like that for a little bit, and then have a single, intense, bright pink flash that lasted about 1-2 seconds before fading. When it did fade, the lamp acquired its normal colour (sort of like a signal to the end of the warmup period).

Strangely, I have noticed, like suzukir122, that when one lamp flashes, it seems like the others do as well. Like they all flash or none flash. I also noticed it with preheat fluorescent that are all on the same switch. Sometimes they are blink-happy and sometimes they barely flash, but it seems like all the lamps on the circuit do the same at the same point in time.

Never. I filtered through lots of CFLs at the thrift shops here, spectroscope in one hand and a mini tesla coil in the other, but i've never encountered any halophosphate CFL.

The discussion about power factor and the 'capacitive' load of LEDs brings up a point. Many years ago, I recall it being speculated on here that the proliferation of CFLs and their less-than-high power factor would cause a noticeable strain on the grid. Has this been absolved in the age of LED?

LEDs make the situation better, because they're such small consumers. For extremely small power consumption levels - think phone charger, LED lamp - there are no demands for power factor, at least not in the EU.
For bigger power consumers like PCs, you'll often find the words 'Active PFC' on the box of the power supply. One basic desktop PC draws as much power as 10 LED lamps of >1000 lumen. One gaming PC as much as 50 LED lamps. So therefore, it's much easier and more affordable to focus on those devices that really make an impact.

Nicer LED bulbs have a power factor correction circuit despite not needing one per law. There are driver chips that do it automatically. Big Clive has reviewed a couple of those.

In the past, capacitive loading of the grid has never been an issue. Inductive loads have been much more important to compensate. Our inductive street lighting ballasts are supposed to come with a compensation capacitor, and professional power users with giant motors also have to have giant banks of capacitors to compensate. So if individuals would use CFLs, it would only be beneficial because fewer of those expensive capacitor banks would be needed.
If there would be an excess of capacitive load on the grid today, the operator can just say 'Hey company, i see you have a big 500kW motor. Usually we demand you compensate that for 100%, but because of local grid conditions, we would like you to only compensate it for 50%'.