I was wondering if anyone had any advice on this point.

I had a falling out with a couple of people about a year and a half ago (basically a culmination of my BPD and an extremely stressful situation, not helped by their actions either and some extremely hurtful things they said and did), but unfortunately we're still in the same social circles. We don't talk to each other and I have apologized to both of these people since, and I completely leave them alone and don't talk about them to anyone, but whenever I see a comment from them it just makes me immensely angry and upset and brings back all the feelings I had to run through in therapy.

I do have them muted and I don't go looking on their profiles or anything like that - it's usually just coming across a comment somewhere by accident (like on a mutual friend's post) that will trigger it.

Do you have any tips for calming down/not getting so angry when it's unavoidable that sometimes I will come across this? It usually sends me into a bad and depressive mood for a whole day before I can "come down" from it.