In T244635#6081812, @Urbanecm wrote:

I've tried to reproduce this a couple of times, with User:Martin Urbanec (test). That acount has no special privileges (besides being accountcreator+autopatrolled at cswiki). I haven't managed to reproduce this issue. You can view my screen at https://ctrlv.tv/IWdw. I have cleared cookies from *.wikipedia.org between the attempts, to make system think I'm not logged into zhwiki, and to let SUL log me in.

The latest victim of this issue successfully edited through 2017 wikitext editor with no confirmed flag. Detailed information are listed below:

Desktop view
IP blocked globally
Local IPBE
No confirmed flag
2010 wikitext editor
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Unable to submit, logged out on previewing and publishing