test_account_

This is almost definitely not going to actually allow tweets to be any longer.

My bet is that it manifests as some kind of text attachment. Just as you're currently able to attach images, video, and all sorts of random junk via 'cards', you'll now be able to attach a text post.

Does anyone have a guess as to how they hoped people would read this?

Surely they imagined it communicating something other than "we're mad we had to pay our taxes".

There are a huge number of cases where application icon (favicon) and corporate logo are not the same thing. For example, Google.