~10+ years ago,
bpdrecovery.com was more active. It was structured similarly to here, as an anonymous forum/message boards, with links/articles/resources. Many staff members here considered it reputable, as it focused on personal growth and responsibility, not blame or victimhood. They may have pivoted to Facebook or another platform, I'm not sure.
While I don't have experience with
Emotions Matter, they look much more current (Facebook page updated yesterday), and appear to offer many different groups, including peer support, grief, education about their groups, a Facebook page, and in person events. So, I would surmise that there are pwBPD who acknowledge and maybe embrace their diagnosis, and engage in peer support and advocacy.
It's possible that pwBPD might attend
NAMI Connections, though those groups aren't for pwBPD specifically, but for general mental health conditions.
Each pwBPD is a unique individual, so your H may be having an experience of BPD different from those who are able and willing to engage with peer support. It's interesting that you mention that he perceives his feelings as mystical -- that may be "working" for him at some level, to provide emotional protection.