I haven’t been on since June, but I noticed it for the last 1-2 years or so. Especially on the smaller subs where any given comment would only get a handful of upvotes. Someone would write a long helpful explanation, I upvote, and nothing happens. The score would stay at 1 or whatever.
It’s not like I was spamming votes either. I would make a point of only voting on one comment per post so my vote would count. But it was still usually 50/50. Vote fuzzing was there for years, but this was different. The comments that were less popular seemed to be affected the most.

They have been for a while now. It started before the API thing with subreddits that were basically mirrors of English ones. But (badly) auto translated into German.
A few weeks ago, the Google results got flooded with auto translations. You can still find stuff that was written in German, but you have to limit the search to German subs (site:reddit.com/r/de, for example).
Or check the sub name in the search results. If it’s in German, you should be good. If it’s in English, or if it doesn’t show up at all, it’s usually a machine translation.