Have a look at the revisions of http://stackoverflow.com/revisions/1230618/listhttps://stackoverflow.com/revisions/1230618/list, in particular the formatting-related edit I made (edit 2). The formatted text contains spurious newlines and indentation errors (not to speak of the randomly inserted HTML escape sequence). Even deleting the newlines and re-inserting them didn’t help.

EDIT

Minimal example that still exhibits the buggy behaviour:

1. Item

    something
        foobar<T>
   

Source (displays exactly right):

1. Item

        something    
            foobar<T>

Another example, from an old posting of mine that worked before, but is now broken: Coalescing regular expressions in PHPCoalescing regular expressions in PHP

Notice how the posting’s source code ends on “<strong&”. Unfortunately, I can’t reproduce this bug here since the code looks fine in preview (click “edit”“edit” to look at it there); only the normal display is wrong, suggesting that the server-side Markdown processor has an additional bug.