There is a plan to get this fixed, by one of a couple of possible options, including:
-Obviously, putting a subject line on comments fixes it. Adding the post title as a default subject line to all comments, similar to what you suggest, would help a lot.
-LJ managed to get Gmail to make a special exception for them, so LJ notifications thread intelligently. If DW can get hold of someone with enough power at Gmail, they can get a similar exception and then it will work properly.

You can rest assured that it is also frustrating several key members of the team, so I doubt that they will be slow to get it fixed.