I personally use a different, but still perfectly compliant suffix character. So just simplistic +suffix filtering isn’t complete. I’ve also considered using a double suffix and having the first one be required, so if someone cut off all suffixes it would go into junk anyway.

Regexing them out will break mail deliverability if the mail system doesn't do plus addressing. And you cannot know from a third party perspective if someone just likes putting plusses in their email address or if the plus is for plus addressing.