Hello there~
I don't know why, but YouTube LOVES preventing me from making comments. If I don't reply to you, chances are YT is stopping me from it. I can technically write a comment, but my comments don't always become public. They only show up on my screen (and sometimes they disappear even on my screen somehow). It's annoying as hell when you spend a long ass time writing a comment only for it to not be visible to others. If you expect me to reply to you about something but don't receive any reply from me, please assume YouTube is preventing my reply from becoming public.
There's one exception to the above: Please don't try to continue a discussion I had with someone a year or more ago. Unless it's something that I'm truly passionate about, I usually refrain from replying to that type of reply to me. When I haven't written anything for a year, it's probably because I consider the discussion to have ended, no matter who was right or wrong.