After I installed flow

Which version, on which MediaWiki version?

I don't know if it is related, but in this comment: https://www.mediawiki.org/w/index.php?title=Topic:Sqd8qg7l54ih29v5&topic_showPostId=sqd8qgcfqx72z629#flow-post-sqd8qgcfqx72z629
Quiddity's talk page rendered as red when writing the post, rendered as blue when saved, and renders as red when you click to edit it.

In T115201#1726321, @Alsee wrote:

I don't know if it is related, but in this comment: https://www.mediawiki.org/w/index.php?title=Topic:Sqd8qg7l54ih29v5&topic_showPostId=sqd8qgcfqx72z629#flow-post-sqd8qgcfqx72z629
Quiddity's talk page rendered as red when writing the post, rendered as blue when saved, and renders as red when you click to edit it.

Interesting. That might be a VE bug; I'll file it separately.

In T115201#1726333, @Catrope wrote:

In T115201#1726321, @Alsee wrote:

I don't know if it is related, but in this comment: https://www.mediawiki.org/w/index.php?title=Topic:Sqd8qg7l54ih29v5&topic_showPostId=sqd8qgcfqx72z629#flow-post-sqd8qgcfqx72z629
Quiddity's talk page rendered as red when writing the post, rendered as blue when saved, and renders as red when you click to edit it.

Interesting. That might be a VE bug; I'll file it separately.

Sorry, I spoke too soon. It happens because [[mw:User:Quiddity (WMF)]] doesn't actually exist (note the "create" tabs in the top right, and the lack of a history tab) and the content you see there comes from his global user page on meta. There's a trick that GlobalUserPage uses to make links to such pages appear blue instead of red, but VE doesn't respect that yet. That has already been reported as T72123: VisualEditor redlink detection should obey Title::isAlwaysKnown (so that links to Special pages, EducationProgram pages and GlobalUserPages render correctly).

Also, to answer your original question, that problem is not at all related to this bug, even though it appears similar at first (red link to user-related page that shouldn't be red).

In T115201#1718466, @Aklapper wrote:

Which version, on which MediaWiki version?

mediawiki 1.25.1 and Flow tarbal Flow-REL1_25-576f705.tar.gz (Flow has no version in the Special:Version page).

Possibly related to the problems/fixes seen in T78102: Flow-ified talk pages appear as redlinks even when the Flow board has content. ?
@matthiasmullie possibly you can give brief advice?