The key difference between manifest V2.0 and V3.0 with regards to uBO is in V2, the extension has direct access to the browser’s process in making web requests and can make direct changes to those requests. V3 instead requires the extension to declare a list of urls and the browser will act on the extension’s behalf. This is a very simplified explanation that isn’t in any meaningful depth and misses a ton of nuance.

The outcome though is V3 makes it significantly more difficult for uBO to achieve its goals for its users. It is a downright and explicit downgrade, and when Chrome fully moves to Manifest V3.0, uBO’s ability to serve its core functions will likely be diminished.

The “numbers” are called Discriminators and served a variety of purposes:

• Identity wise it meant multiple people could have the same username text. If you wanted to be John, you could be John#6754 and someone else could be John#1298 and both of you could be John! Now there is only one john.
• It provided parity. EVERYONE had it, therefore no one is better or worse than other excluding particular number combinations. If you were John#5363 and hated the discriminator, well everyone else had one, versus someone behind john, and then someone having to be john_87 because there’s already a john

You argue that being able to use effectively the same username everywhere is a good thing. The unfortunate reality is the rollout Discord used alongside the limited number of permutations (combinations?) of short usernames makes this impractical. For example, a friend largely goes by a 4-char username, and the switch by Discord means they can’t use that 4-char username on Discord anymore. It’s easy to say like “well, just add something to the end”, but that is exactly what discriminators did.

At the end of the day the benefits weren’t as compelling as the losses (it would suck to have one’s identity impersonated or username stolen, or now most folks with short usernames have to stop friend requests cause they are getting spammed with them, or the fact these accounts are valuable and can be sold).

It is understandable that some people don’t really care about the matter and that’s fine, but it doesn’t make the frustrations others feel less important.

Reddit doesn’t (at least as far as I know) store a history of edits, so what is saved on the database is what your comment literally is. The reason people suggest overwriting comments is because the comment itself has value (for a variety of reasons), so overwriting the comment with something valueless (in the sense that it has no value for Reddit) is better, so the database itself is updated with that valueless comment.

After that whatever you do with the account is up to you.