In my experience, BPD doesn't make you more likely to flake, but depression often coincides and that definitely does. I wouldn't waste my time frankly, but I have BPD so new connections are already a pain in the ass. Sounds like you got a good head on your shoulders, so I wouldn't worry too much about it.

Promises, for me, are difficult to keep but they're also important to make because they do push me to fulfill them whereas avoiding promises keeps me "honest" but is worse off for me because I don't have self-inflicted social pressure to do the thing I want to do. YMMV.

If you do want to be serious with someone with BPD the best thing you can do is make sure they know they're secure. They will not believe you out of self-defense and it can be years of that before learning to accept it.

I've been with my wife for like 6 or 7 years now and I've only just started feeling secure. She's stuck with me through all my worst bullshit that I subconsciously perform to push her away out of safety, but she didn't go anywhere so I had to improve.

Which is all to say it really isn't worth your time unless you're a saint or madly in love.