I’ve experienced this too, the most insidious are burying links in punctuation with their edits. Instead of generating clicks from the victim site they seem mostly concerned with creating inlinks and are oblivious to the nofollow being applied to said links.
The other more worrying trend is wiki edits, unlike posts and post edits these don’t appear in the user activity, I can only tell that it has happened because they’ve received a wiki editor badge, without ever posting a wiki post.