Characters in Mathematical Alphanumeric Symbols get stripped out, it seems. Or does it just choke on them? There should be some here:
There were other tests in here, in which I determined that full-width and Cherokee both work, and noted that I can make blank posts — but I added some characters that it does not like above, and now the records of those tests have vanished into the ether, lost like whichever ephemeral thing the stock phrase which I cannot currently remember contains.
It appears that they get stripped out somewhere between 'preview' (where they display) and 'post' (where they do not). The same applies when attempting to add the characters to one's custom user title field: they display on the 'finished' screen, and then disappear.
After this point, there should, but will not, be a series of Fraktur letters, followed by those in the standard script which Hitler favored (really! Hitler! denazify Latin back to Fraktur, you fascists!):