I was trying to edit this question and it gave me this error:
The other question is Java heap space out of memory. Indeed, it has an identical title, but if I can't submit an edit because the title is identical, why can the OP ask a question with an identical title?
Just as I suspected, nothing is checked when I submit the question. See my test question (you need 10k on SO).
Now try to edit it, without changing the title and watch it complain.
It seems like the filter has been disabled.
FWIW I think this is a huge waste of time and resources. When this thing was on I had to wait a few seconds for my edits to go through. This also won't make people write better titles, they'll just get annoyed and reorder the words, add punctuation, etc. just to get around the filter.