bingle-admin wrote:

The WMF core features team tracks this bug on Mingle card https://mingle.corp.wikimedia.org/projects/flow/cards/670, but people from the community are welcome to contribute here and in Gerrit.

http://ee-flow.wmflabs.org/w/index.php?title=Talk:Sandbox&workflow=050b9efcf0e3f00fc8b1fa163e68c4ac is another topic with a phantom (anonymous?) user, though it doesn't have the weird <pre> tag in the topic box.

Change 104930 had a related patch set uploaded by Matthias Mullie:
Automatically run FlowSetUserIp on update.php

https://gerrit.wikimedia.org/r/104930

There's a maintenance script: FlowSetUserIp.php, which will move all the ip data to the newly created columns.

This script was not automatically being run on update.php; I've submitted a patch to do so (https://gerrit.wikimedia.org/r/#/c/104930/).

For deployment, this is not a big issue, since update.php is not run. We'll have to make sure to manually run this maintenance script, though (and I've submitted another patch that fixes a minor bug in it: https://gerrit.wikimedia.org/r/#/c/104927/)

Change 104930 merged by jenkins-bot:
Automatically run FlowSetUserIp on update.php

https://gerrit.wikimedia.org/r/104930

Running FlowSetUserIp did clear it up.

The pre tag is due to the flow-topic-participants going through parse(), and in wikitext leading blanks format text as a <pre> tag. You can see this using eval.php:

echo wfMessage( 'flow-topic-participants', 2, 2, '', 'second person',

'third person' )->parse();

prints

<pre>and second person
</pre>