Well, you are a moderator (note the symbol below your avatar), "a selected group of long-time MaplePrimes users with a reputation for positive contributions." - see https://www.mapleprimes.com/help/moderation.
There are some good reasons to edit others' posts; removing copyrighted content is one I've used. Another is removing duplicate copies of posted worksheets.
There are guidelines on the cited page. One of them is:
"In general, try to avoid making spelling or grammar changes unless they are particularly egregious, but feel free to edit message formatting if it messes up the display of the page." Since I don't think @acer's grammar was egregious, perhaps you are in violation :)
But seriously, this policy does not seem to have led to much difficulty.