Yes, they can disable comments on any posts that are not breaking the rules, but the comments are very often.

@LunarEclipseSP i remember there's a debate about Chinese politics there, i think that's why the comment and upvote is disabled

@LunarEclipseSP Ohh, I thought it was a bug because it's rare. Thanks

It is not a bug, it was the intentional site design. the comment, and the upvote is just disabled by moderators, I'm sure there is used to be some debate and argument there.