Here's a link (from my inbox) to a comment that's initially hidden:
Despite hidden comments being shown (to show the linked comment) the "Add/Show 2 more comments" link is shown.
In the related question (above) it was noted that someone deleted a comment which may have mucked things up temporarily, I'm wondering if this is the case this time too.
Even if it is because of a deleted comment, should it be fixed so that we don't get the error/misinformation at all?
One additional note: It appears this will only happen to me (the one who commented).
Possibly it's triggered by the "Avoid extended discussions..." message its self being implemented as a comment (that would only be applicable/visible to me).