Anything that discourages them. For instance, immediately reverting their edits for whatever reason[0] rather than fixing them or suggesting a fix; nasty messa

Anything that discourages them. For instance, immediately reverting their edits for whatever reason[0] rather than fixing them or suggesting a fix; nasty messages posted to their talk pages criticising their edits; drive-by tagging pages they created with lots of boxes indicating that their article is bad and/or inappropriate. I was a Wikipedia regular for several years, but these days it seems like if I do anything more than basic spelling fixes it becomes an unpleasant experience. [0]Lack of notability and lack of source information are the two big ones there.