Make sub anniversaries make sense
I have a few issues with sub anniversaries:
(highest priority) When shared, sub anniversaries show up in chat & the activity list as a regular sub, even though the popup to share an anniversary vs subbing is different & they are obviously separate events, they just don't show as such. Confusing!
Because of the above, there is no real celebration of this person's anniversary i.e. initial sub date. Streamer isn't prompted to say 'yo congrats! you've been here so long!' or whatever. Why even have anniversaries at all?
If you DO want anniversaries to be special, make them? Like, make them yearly instead of monthly (honestly, why would I care that I first subbed on the 23rd of the month 17 months ago?). Give the person a little birthday hat flair on their sub badge for a while. Maybe even make follower anniversaries a thing too… just some ideas. Would be nice for community feeling.
Your sub anniversary isn't mentioned anywhere to anyone other than yourself. Again, if they don’t show up as such in chat OR anywhere else, why allow people to share them? Why do they exist? Even in a small way, it could be shown below follow date when you click someone in chat? Just show "First subbed on ..." with the other sub info that's already there.

Thank you so much for the level of detail and organization that you used to present this idea.