I agree and disagree as well. There are a lot of posts that I don't really understand but that someone put in a lot of time and effort to make and if I manage to get through the whole post and still don't understand but know that once I get more knowledgeable on the subject (like cryptocurrency) things will make more sense to me... for those types of posts I generally comment something like "great post, wish I understood it more" or "nice post, someday I hope to make more sense of it" and I don't see anything wrong with those comments but I also don't expect to be up voted at all.

Now don't get me wrong, those of us that type a "nice post" or "great post" type comment shouldn't be expecting an up vote for those comments but we should be able to say those comments without feeling like we are doing something wrong.

When you don't really understand the post, either because its on something you don't quite get (again like cryptocurrency for myself) or perhaps its in a language you don't understand but the pictures within it kind of give you an idea of what the post is about, then really the only comment you can make, if you even make one at all, should be "nice post" or "good post" because you can't really say anything else if you didn't really understand it.

Of course that is just my opinion. :D