Not convinced that this is correct; yes, you /can/ have a valid page at a web site, but still want to link to the external one. For the most trivial example, "amazon.com" is both an article (on enwiki) and a valid external link. Therefore I'm minded to WONTFIX this.

Also, I'd note that there are timing issues (as the list is created before the suggestions are returned), but those are minor.

I am not proposing ANY changes to creating a new link. So when you mark the text wikipedia.org, yes you should be provided with page and the url in the picklist.

My suggestion is about the confusion that occurs when the link already exists and already points to an internal page. I believe that then the chance that users want to validly change it to an external http URL are very small and not worth the confusion. The enhancement is about avoiding visual clutter and avoiding accidental mis-selections. And in those cases where you do want to change an external link to an internal one: you can still do it, only not with the pick list.

I am not sure I understand the timing issues you mention, since the web page suggestions are always non-sense suggestions, just prefixing the text with http, so it seems easily suppressible. The ajax responsible for possible pages is a different story, but the visibility of that is not under discussion.

This refers to behaviour that has now changed such that this is no longer actionable, so marking as INVALID.