The 280 char limit seems arbitrary, given you cant even keep the about page within that limit: https://textlog.cc/about
If you are going to limit it to short posts, maybe the length of a short post is the length to limit it to, rather than emulating the 2xSMS of every twitter clone?
Other than that, it looks really clean and neat - I just dont think being 280 chars adds anything other than resulting in people posting with pagination as per X 1/3.
It needs to be short - there is already a limit that worked well - why bikeshed it more?
I like the idea of a shorter character limit as it nudges users to a specific mode of interaction: short thoughts/updates and not long-winded soliloquies. It's signalling that interaction with this platform doesn't demand much of your time or attention. I don't know what the about page has to do with it, but you have to draw the line somewhere.
That said, I'm not a social media user besides HN I guess.