I looked in the rules section and I didn't see anything about editing reviews, so if it is somewhere else on the site I didn't think of, I apologize in advance. I recently looked over some reviews and noticed two of them had stupid spelling grammar mistakes (Kvelertak and Neige et Noirceur.) Would it be considered pointwhoring if I edited the review to fix said mistakes?

No. You won't be granted any additional points for your edit anyway.

Well, I have received double points when I've had little edits I've needed to make...?

It happens every once in a while by mistake. But when it does, it's not intentional in either party's case, so don't worry about it. You won't be at fault if it happens, anyway.