what happens if you post videos on a FB pages post A LOT in the comments?

[Rstjstj]

can you get banned off FB for posting a youtube video many times in a group's comments section on a post?

[Needful Sinner]

Of course. Facebook, or any web server don't need any reason to terminate service - it's their site and your Facebook is their property, not yours. They don't need a reason and can do whatever they want with what is - their website and their server.

That said you most definitely can be banned for spamming and/or harassment - why would Facebook even want you as a user if you're just going to me ruining their image or making things difficult for other users - no different than if you make prank phone calls your phone company has cause to terminate your account or act like a goof in a restaurant you'll just get shown the door, it is a misuse of service.

FYI - you could delete such posts, but if the person receiving them isn't impressed and reports this as spam or harassment, and Facebook investigates - everything you've done is logged on their servers... every post, every comment, every deletion, every keystroke.
Deleting only makes it invisible to the public, it's still on record on the server's logs.