What content am I being blocked from editing and why?
Was trying to edit the following question to fix the broken URL:
Upon submitting I get the following error:
Oops! Your edit couldn't be submitted because:
* Sorry, posts can't contain that content.
* Sorry, post titles can't contain that content.
I literally just fixed the URL and added tick marks around "C:", and the error message doesn't make it clear what "that" content is.
What happened? / What did I do wrong? / Something broken?