This is a great plug-in, especially since it supports so many languages!
However, I found one little problem. I set it to replace single quotes with ,‘ so e.g.
'Ich habe Sergius gekannt', sagte er.
,Ich habe Sergius gekannt‘, sagte er.
in accordance with the convention for German.
However, there are contexts in which the character ' occurring at the end of a word represents an apostrophe and should be replaced with ’ rather than ‘. E.g.
'Ich habe Sergius' Mutter gekannt', sagte er.
,Ich habe Sergius’ Mutter gekannt‘, sagte er.
I realize this distinction is difficult to make with simple rules, but given the amazing work the developers have put into this plugin, I guess they might like a challenge. :) Matching opening with closing quotes comes to mind (so ' isn't interpreted as a closing quote unless there was a matching opening quote).