Post editor; Heading not working for less than 3 charactors

[11122 (徐徐浩)]

Hello, I have some questions with the Heading.
When I have a word less than 3 characters, the Heading does bot work with it. For example:

I have to add a “-” to make the heading apply:

I am not sure this is a bug. Anyone could explain this?
Thanks

[codinghorror (Jeff Atwood)]

Seems to be a bug specific to Marked

http://johnmacfarlane.net/babelmark2/?normalize=1&text=in --

[sam (Sam Saffron)]

Fixed now:

in

CommonMark testing started here!

Per our migration plans, I just enabled markdown.it at Meta. It is an excellent CommonMark compliant engine. I expect quite a few edges to be found during this period of testing. Do not open bugs about the new Engine, just reply here. I/we will be updating the top post here with the list of issues and striking out stuff as it is fixed. Current known issues (to be fixed) Onebox vanishes after you start typing and works not-super consistently pendin…