CommonMark is a bit more strict than the previous markdown flavor.
One of these cases is the markdown for headers to generate an H1, H2 or H3. A
# on a new line followed by text was all that was needed, for example:
There was no requirement that the # needed to be followed by a space. With the switch to CommonMark this has changed and a space is mandatory.
I was a notorious no-space user.
Is there a SEDE query that can show me the posts where I most likely used header markup that is now rendered incorrectly?