My favorite instance of this was Mailgun, who html encoded the apostrophe, and then html encoded the resulting text.
O'Bryant -> O'Bryant -> O'Bryant (screenshot: https://twitter.com/obryant666/status/1163638029212250112/ph...)
O'Bryant -> O'Bryant -> O'Bryant (screenshot: https://twitter.com/obryant666/status/1163638029212250112/ph...)
I'm also the person who gets irrationally annoyed at web forms that barf at my username+tag@example.com email address usage (+ signs being valid in the username part), so I can certainly relate to the ire, too.