[TeMPOraL]

Even with services that lived over a decade, it's not clear whether messages were accessible for all that time. E.g. Google Talk/Meet/Whatever seemingly lost all messages before ~2013. Links to Facebook posts tend to die quickly, as both users and Meta itself seem to constantly play with privacy features. Etc.

[tsterin]

I really like your point (I'm one of bbchallenge maintainers). I think that Discord is close to optimal for us in the short term, but bad for the reasons you and other have mentioned mid/long term.