Confirmed. This also happens if you type too quickly and press enter.

I am raising the severity on this, because it is not just a display bug, but also causes the intended link target to be ignored -- if the user confirms the link with enter, only the link title is used and the link target is quietly discarded.

(This happens particularly often on Opera for me, by the way. I haven't yet investigated the issue.)

Change 72849 had a related patch set uploaded by Robmoen:
Be sure lookupMenu input is focused before showing inputMenu.

https://gerrit.wikimedia.org/r/72849

• Bug 51077 has been marked as a duplicate of this bug. ***

(Cite bug 51077 comment #0)

Created attachment bug 51077 12810 [details]
Screenshot of ripped-apart link inspector

I can consistently reproduce the following:

• Select an unlinked word
• Create the insert link button (with intention to turn the word into a link)
• If you hit Return immediately after (before it has finished opening) it

will
replace the focussed node with a new line. Though that is a separate bug and
arguably an invalid use case (why would one be pressing Return at this point,
the user hasn't even seen the options yet. It interpreting it as intend to
replace the node isn't entirely unreasable, but that's a separate bug - bug
51075).

• At this point the link inspector dom has blown up. Part of it is gone, and

the other part is left half-way across the screen at a seemingly arbitrary
offset (see attachment).

Change 72849 merged by jenkins-bot:
Be sure lookupMenu input is focused before showing

https://gerrit.wikimedia.org/r/72849

Fixed and will go out soon.

Not completely fixed; see bug 51415.