A picture of a kitten in the appropriate general forum or a statement agreeing with the general opinion on a top comment on some politcal forum will get many times more Karma than a post on an expert forum that took 30 minutes to validate and write and is anchored on a decade of domain expertise.

Beyond it's utility (for commercial social media sites) as a gamification element (a score, which incentivises people compete with each other in producing easilly digestible content that pleases the general population in a forum - which, note, doesn't mean its correct, well researched or anchored in genuine domain knowledge), Karma, at least as done in Reddit, is near useless.

Maybe some kind of per-forum Karma or just a per-forum summary of the reception of past posts for a user might be useful, but "score"-Karma just indicates the ability to produce lots of content (so, produced quickly, hence almost certainly not validated) which is popular in large forums (which are invariably the generic ones).