So here's what's happening:

The default behavior of the forum is to NOT change the anchor text to the title.

We use a third-party plug-in to re-write those links when the pages loads. There are two reasons for this. First, it is a better user experience to be able to read the title of the thread before you decide if you want to click on it. Second, it gives more descriptive anchor text so that spiders can better understand the content on the linked page.

When you load a page, vbulletin builds the page with the default behavior. This page is then passed through the plug-in, which re-writes the page with the new behavior. When you use the quick editor, the page doesn't refresh, so it never gets passed through the plug-in. The result is the link in the page following the default behavior. Now, if you refresh the page, the page is re-generated by vbulletin, and properly parsed by the plug-in.

So, the short answer is that only the person who made the edit will see the incorrect anchor text, and only on the page load that the edit was made.

This wouldn't be a "new" bug, and it wouldn't be a bug that we would be able to fix, as the edit function doesn't pass through the required hooks to fix the behavior. Regardless, the user who made the edit probably already knows the topic of the thread that they linked, so the enhanced functionally isn't completely necessary.