I'm not entirely sure if this is what the fix was about, but in 1.5.3 it is possible to select a file in hg repo, click edit, make a web commit and that will create a separate head. The parent of the new head is the revision when the file was last changed. The other head is the tip. So in essence it works like anonymous branching.
It works, however, for new files. The parent is the tip and no new heads are created.