Red Cyclops, thanks for starting this thread, as this subject's been on my mind a fair bit recently. I have both diagnoses, and OCD as well. While the OCD stuff is clearly over the diagnosic thresholds (uhh, hence dx, lol), it is not severe (and my heart goes to out to those for whom it is). TG it's not, because BP is definitely the "ringleader" of the Brain Forces, and there's already enough duking it out up there as it is. Back to ADD (haha, just realized the unintentional but telling nature of that). Like you, I've been endeavoring to figure out where one ends and the other begins. I know the constant vs. episodic distinction of course. It's more like, "Which one of you is wreaking this havoc right now?". Probably a fruitless exercise.
Due to a couple of misconceptions I had about ADD (and yes, I know that abbreviation is not the current nomenclature, but think they made it much clumsier with not nearly enough net gain to warrant it), and not wanting to have any additional diagnoses, I tried dodging and "reason" making to explain it away. Also, I had come to have a number of coping strategies through the years to help mitigate its effects --also a help to denying it. Learning more though, I did concede. The meds have helped. Having lived for so long with it, I didn't really realize how many "stations" were playing till the meds quieted it down. Wow. It was quite a revelation.
(BipolaRNurse, the version I know is, "Oh look! A chicken!" Haha, that is SO hearing me talk.

And even my writing -- realized an aspect one day, and dubbed it "parenthetical style". While I do make efforts to stay on topic better in writing (which is easier because it is not immediate, like speech is, and can be "tidied up"...then, "why,hello, OCD", I very often spend hours and hours on editing and re-editing over and over and over...), I find it
very difficult to express my thinking w/o it.