Sometimes, when you paste from the visual editor in one window to the visual editor in another, words get jumbled into a bunch of gibberish.
Example:
"Prior to this ban, there were debates" was changed to "T Prior to teis ban, thre hweredebates"
https://en.wikipedia.org/w/index.php?title=Prospect_Park_(Brooklyn)&diff=846763975&oldid=846446246
Reported by @Epicgenius at https://www.mediawiki.org/wiki/Topic:Ufujo8is07ouclhe