> This reminds me how I've had to tell people to try to type better and nt us wird abbrvs, even if it means they can type it faster.

You can also teach those people about text expansion software. macOS and iOS have it natively, though if I’m not mistaken it doesn’t work properly in non-native apps such as Slack. Alternatives like Alfred should work anywhere. That way they can keep using their abbreviations to type faster, but others won’t have to deal with them.

> It's very likely that proper punctuation and capital letters help the reader

Can confirm. Not using proper punctuation and capital letters makes reading less fluid. I’ve stopped caring about posts and comments that do that—if you don’t care enough about what you wrote to do the most basic of courtesies (and sometimes even fighting the auto-capitalisation that’s done for you) then why should anyone else expend the effort?