thanks for linking that, it was super interesting!
i suspect i had some HITs come back from a server farm a while ago, when we were getting work done in spanish. a few workers submitted their work in english (despite the entire task description & instructions being entirely in spanish, in addition to specifying that the responses needed to be in spanish) so i had to reject their work. two workers wrote to request that we reverse the rejections, but their messages were completely identical, barely comprehensible garbled english. i 86'ed those two, and for the later rounds of that task i changed the location restrictions and it wasn't a problem again? i thought it was super weird, but it makes way more sense after reading that article