I think knowledge is power so I think it's great that people learn and understand the concept of "favourite person" and "splitting" but Ive noticed on this sub it can take on a life of its own. It goes from being just a word to describe an action to a word to describe all your problems. I think putting such strong emphasis on these terms especially when you label another human being with these things is detrimental. 

If you use the word FP to describe your boyfriend or friend you're taking away the humanity of that person. Instead of being a friend theyve become a product of your disorder. They are no longer just a friend with their own wants, needs, and wishes they are now an FP. A direct connection to your disorder and ultimately a determining factor in your happiness or misery. Of course everything they do is going to affect you if you've put that label on them. I'm not saying FPs aren't a thing but I also think many people experience strong feelings for people without it being disordered thinking and I think a lot of people experience bad feelings towards ppl when they let them down without it being disordered thinking. I think by labeling FPs you are sentencing that relationship to always be disordered instead of working to normalize it. 

Same idea goes for splitting. It's a term health professionals can use to describe a pattern of behaviour/thinking but not everything you experience as black and white will be a symptom of BPD. Lots of people see the world as black and white. Its a lesson many people have to learn and instead of combating this type of thinking I see people experiencing anxiety and stress because they see everything they do as splitting. The label causes more trouble then the actual issue. 

I personally think it would be beneficial to throw these terms out the window and just take each situation as they are. Use the appropriate DBT skills for the moment and forget the lables. I think its easier to hide behind a term to describe your behaviour then to just look at the situation as what it is and sort it out. I do not use these terms personally because I do not believe all my behaviours are BPD  behaviours. I think many of my behaviours and emotions are valid and normal. I do believe by not falling into this label game with my emotions it is easier to normalize them and therefore more effectively deal with them as well as feel less judgement and shame towards myself. You are not borderline personality disorder. You are someone who has borderline personality disorder. Not every action, emotion, and thought you have is due to your disorder and I think labelling all our emotions with such strong BPD labels can leave you stuck in a world where you feel you are not normal and your emotions/actions are all problematic. This is not the case. Not the case at all.