I don't know what the reasoning was when the ability to undelete comments was introduced and restricted to mod-deleted comments. Whatever it was, that's how things work right now.
@SimplyBeautifulArt No idea. The workings of the review queues aren't easy to understand.
@SimplyBeautifulArt I'm not sure whether I understand the question. There is calculus tag. And there is probability tag. (And, BTW, there is tagging chat room - although hardly ever somebody comes there.)
This may not apply: But: When the rep you gain is from another site other than MSE, you'll see the green notification on the top bar, but if they weren't gained on MSE, they won't count towards MSE rep.
@SimplyBeautifulArt That's weird, indeed. I tend to simply keep a tab of my profile, and click on reputation to see changes to MSE rep. which typically more up to date.
All I know is that the +100 is for an association bonus, which allows you, and any user established on MSE, to join any other SE site at $101$ rep, rather than at 1 rep. That's all I know, but I'm sure others, quid, a mod, Martin, can clarify things far better than I can.
@amWhy if you would like to question my comment deletions, you can mention something here. But these are off topic on that thread, so I will delete them there.
For what it's worth, I didn't overrule Jyrki anywhere. He left, there were additional off topic comments. He mentioned uncertainty in private moderator chat. I step in.