In a reply, type:
* fasd <insert link> type bogus as link address, <insert the red link> keep typing
* Switch to wikicode
* Switch back to VE
* Switch to wikicode
* textarea contains: `fasdf [[/w/index.php?title=Sfd_fasdfas&action=edit&redlink=1|sadf]] sd fdsafadsfsd`
superm401: "It's probably because of our redlink "fixer"... (Which normally works well, but we only recently re-enabled VE, so it's probably a bad interaction)."
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Another variation (but probably same cause):
Entered (among other things) `[[Adrines]]` in wikitext, got `<a href="/wiki/Adrines" title="Adrines" rel="mw:WikiLink" data-parsoid='{"stx":"simple","a":{"href":"./Adrines"},"sa":{"href":"Adrines"},"dsr":[52,63,2,2]}'>Adrines</a>`. You can see that the href has been normalized (I think by WikiLinkFixer), and when Parsoid comes up it's already confused (it thinks the page name is /wiki/Adrines).
Then when switching again it's `[[/wiki/Adrines|Adrines]]`. Note this is not a red link, but it doesn't really matter (hence why we renamed it to WikiLinkFixer).