[handrous]

I took it as an example of how fake and political their communication has become, and/or how disconnected a "community" they are. Course announcement that's easy to comment on, 20 pointless "that's great!" replies. Something serious and personal, 0 or 2 (there are two cases mentioned, not just his) because it's a channel for obligatory, performative engagement with strangers, not sincere communication with close colleagues.

It's probably intended to land best with people who are familiar with how communication works in that school/department, and the general atmosphere there, I'd expect.

[lupire]

a tweet eulogy seems like an easy peformative act.

likely he suspects that colleagues are afraid to publicly associate with him because he is too left wing / unapologetically Black / hot topic for Harvard.

[handrous]

Maybe, and maybe the other person with a similar experience is also to be understood as similarly persona non grata, for those with more insight into the circumstances.

This is definitely one of those "could be full of shit, or might barely even be scratching the surface and is actually quite restrained" kind of letters. It's hard to tell without more info.