Anyway, to quote a person's comment, all you need to do is find this hidden Byte Order Mark, and delete it.
Then you can post your comment, with quotes, without it being incorrectly auto detected as "SPAM".
So, in addition to
user censorship (way way way way way too easy to censor other people),
there are some rules that Youtube puts in to catch SPAM.
There also used to
be more rules in comments, when if you tried to post a link, it would
auto mark as SPAM. (this way, YT allowed spammers to THINK they were
posting correctly, but actually, their comments got auto hidden). But now it just gives you an error, out right.