I don't know what's going on here.

The contributions clearly shows you creating the thread:

22:40, 21 June 2012 (diff | hist) . . (+160)‎ . . Nm Thread:VisualEditor talk:Welcome/Not here? Tch! ‎ (New thread: Not here? Tch!)

As does the LQT history: https://www.mediawiki.org/w/index.php?title=Thread:VisualEditor_talk:Welcome/Not_here%3F_Tch!&lqt_method=thread_history&redirect=no

However, going to the thread via timestamp link (https://www.mediawiki.org/w/index.php?title=Thread:VisualEditor_talk:Welcome/Not_here%3F_Tch!&oldid=552738) shows David Gerard creating the thread.

Could be a LiquidThreads bug.

Now that you show those links, I think I know what happened. I was probably manually migrating a thread from wikitext to LQT, by copying the source code to the edit area, and copying the author's signature to the signature field (you can notice the duplicated timestamps, one from when I created the LQT post and another for when the author posted the comment I was copying).

So, it seems Flow is ignoring the signature field I added to the comments (which is where the real authors are shown), and using only the username of who created the LQT page (in the example, it was me). And we have many LQT topics converted from wikitext like this (at least on ptwikibooks), mostly from the transition period from wikitext --> LQT, when there were a few active threads which we didn't want to archive.

As a simple workaround, I imagine the conversion script could just copy the content of the signature field to the end of the comment (in case the signature is different from what it would be in case the author of the comment was the user creating the comment).

Yeah, I can probably solve this by exposing getSignatureAuthor separately from getAuthor, then implementing it for LQT using thread_signature. This is conveniently not implemented in the API, but will be easy to add.

I'm not going to go back and fix the already imported ones via script, but I'll add comments (similar to what you suggested the script did) manually.

FYI: by copying the signature to the end of the comment, it will look like some of the messages distributed through MediaWiki message delivery. E.g.:
b:pt:Tópico:Wikilivros Discussão:Portal comunitário/VisualEditor News 2—2015

Change 217706 had a related patch set uploaded (by Mattflaschen):
Expose thread_signature in API

https://gerrit.wikimedia.org/r/217706

Change 217706 merged by jenkins-bot:
Expose thread_signature in API

https://gerrit.wikimedia.org/r/217706

• https://gerrit.wikimedia.org/r/217706 (branch master): WMF-deploy-2015-06-16_(1.26wmf10)

Change 217984 had a related patch set uploaded (by Mattflaschen):
Separate logic for extracting usernames from picking the right one

https://gerrit.wikimedia.org/r/217984

Change 217985 had a related patch set uploaded (by Mattflaschen):
Show template when LQT signature user differs from author user

https://gerrit.wikimedia.org/r/217985

Change 217984 merged by jenkins-bot:
Separate logic for extracting usernames from picking the right one

https://gerrit.wikimedia.org/r/217984

Change 217985 merged by jenkins-bot:
Show template when LQT signature user differs from author user

https://gerrit.wikimedia.org/r/217985

After conversion, signatures are associated with actual user names.

Two cases

• if a user is not logged in and he edits his signature - that signature will be converted to {{LQT post imported with different signature user|authorUser=198.77.321.1|signatureUser=dragon2}}
• If a user enters ~~~~ as his signature, upon conversion it will be displayed as his signature, e.g. zilant 18:15, 18 June 2015 (UTC)

Steps to reproduce:

1. Login
2. Create a LQT page
3. Click 'Start a new discussion' (using AJAX interface)
4. Enter a Subject and body.
5. Click 'edit signature'.
6. Put the exact text ~~~~ in the signature field.
7. Click 'Save page'.

Appears as:

thread_signature in the database has:

[[User:Other|Other]] ([[User talk:Other|talk]]) 02:24, 22 June 2015 (UTC)

After conversion, I don't get the signature warning. It looks like:

Did you mean if they enter ~~~~ in the body field (rather than in the 'edit signature' field)? That is not supported for LQT either; it tells you not to.

Matt, should we move this back to In Development?

Mattflaschen ,

I re-checked with the exact steps that you wrote - yes, it works fine - the edited signature(~~~~) in the signature field get converted to a proper user name upon LQT->Flow conversion.

Signatures entered as a wiki text in the body - it makes sense not to convert them.