<I don't know what you mean by abusing it but probably people should be aware to keep links out of message subject lines or the content will be hard to reach. At least it can't be reached directly.

I never notice before but if you have only one message, you'll get this in the left column:

Message box (1)

where you can click on the (1) to access the message.

But if the message subject header is a link, the left hand column lists it this way:

Message box Ad That?s me">(1)

The "AD that?s me" is a clickable link taking you to the actual message. So you can access that message from the left hand message area but from your message box it takes you to the outside (or inside as the case may be) link.

Is that confusing? ;)