Good topic with interesting timing. I do like this idea of what remains between episodes being "something else", that potentially is significant enough to be a separately diagnosed condition. For me, I do notice that all sorts of symptoms exacerbate during episodes, including those that are unlikely to fall under the BP umbrella. Their (non-episode) level of interference determines if/what they are dx'd separately. Pretty sure my psych operates that way. Here's why it's of current interest to me... I thought I knew my dxs. But when she filled out some paperwork, one (of the three) was different.(Not insurance purposes, btw, as I don't have any.) On that one, what I thought and what was written are both anxiety disorders. She did not just tack one on with the other. Was it fine tuning? Was it observing one variety as ongoing and independent of episodes, while the other waxed and waned with them? I'll definitely be asking.

As for beneficial or detrimental, I 'd have to say detrimental to tack on more than necessary. Regardless of how it "reads" or makes one feel, each diagnosis has its own parameters. To toss them together/add on because of overlap issues would only confuse the issue because it suggests probable/assumable symptoms that the person doesn't have*. (This is very much a concrete example of why I take such issue with people lumping BP and BPD together.)

(And let's face it... really, how many of us need people thinking we have more problems that we already actually deal with(!) )