I don't necessarily disagree with you in the grand scheme of things. It's just somewhat hypocritical, in my opinion, to admonish someone for saying "lol" in response to, well, let's face it: a completely ridiculous post.

But fair enough. There are plenty of communities online that I am active in that have their own inconsistencies in how they police themselves (whether through moderation or downvoting). I'm not going to take it too personally.

It's not an admonishment. It doesn't mean people think you're a bad person. It just means that if that's all you have to say, they'd rather you said nothing.

Well, if that's the case - why can't one delete a comment after a certain period of time?

I don't know. I bet it's probably an artifact of the implementation - it may be tied to the fact that you can't edit a post after a certain period of time.