I once tried to edit an article about a scientist who had developed a bit of surrounding controversy over his studies in parapsychology. Having no real knowledge of the debate, I didn't add or remove any information; I just felt the introduction had been written in an overtly non-neutral way by a past editor. So, I removed a couple of words like "hoax" and trimmed one or two sentences so that they didn't come off as a character assassination (they had contained unsourced editorializations). Specifics aside, the article had explicitly violated Wikipedia's policies on using NPOV language.

My edits were reverted within 24 hours, and the talk page was updated with an admonition to my IP address (I'd posted without logging in) claiming I'd been implicated in "unsavory" activities that could be found by Googling the IP (it was a dynamic IP, but of course I tried and found nothing) and making vague threats that I should not attempt such edits again. That's the last time I edited anything on Wikipedia.