Last modified: 2014-10-22 18:39:04 UTC
Safari Version 6.2 (8537.85.10.17.1) scrolls down one line for every character I typed in https://www.mediawiki.org/wiki/Help:TemplateData I was not able to reproduce this in Firefox 32.
Update: An editing session may start normally and have this problem appear later, so perhaps I just didn't spend enough time in Firefox to trigger it. I still have no idea how to trigger it reliably.