I've noticed that like other social media, people seem to ++ a comment or a post as a marker that they've read it. It's.. a bit misleading sometimes..

Yeah. It's annoying.

Curious, how are you inferring the intent behind the behavior?

@SortOfTested A ++ immediately followed by the comment itself. I infer it from previous experience with same behavior on other social media websites.

Another factor is congruence between the ++ and the original comment that's being ++'d. A negative or nearly meaningless comment shouldn't get a ++. It's like a code smell - something is fishy. It's like in that movie The Imitation Game, where Alan notices that a German officer and a female alliance officer always end their messages with a specific pattern.