I noticed this recently when working on Evoq Content code (ironically I was removing the inline editing function as Evoq Content uses a different editor). Here was my post to the team:

Whilst testing this I noticed the inline editor doesn’t work in IE11 – I was broadly aware of this as recently I helped a user get Treeview working at http://www.dnnsoftware.com/forums/forumid/160/threadid/497510/scope/posts/threadpage/4 ). It is possible to get some WebControls (http://dnnwebcontrols.codeplex.com/) working by altering the ClientAPICaps.config file, but when I tested with that (by adding a simple to each subsection which covers IE11’s useragent of “Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; MDDRJS; rv:11.0) like Gecko “)), I found the results to be unreliable i.e. DNNLabelEdit works for updating module titles, but doesn’t work for updating HTML content. I’m guessing there is some CSS issues here we could fix, but I wonder if we should bother as no-one seems to have noticed or logged an issue for it.

So it appears that you're the first person to notice it (outside myself) - you're welcome to log it to support.dnnsoftware.com but the reality is that the webcontrols and clientAPI projects are ancient and haven't been updated in years, and I don't know how likely they are to be updated (we'd ideally like to rip them out altogether, but realise that 3rd party modules use them so have left them in place so we don't break their modules)

Thanks a lot for explaining the issue. I'll just do the editing in Chrome instead... ;-) Good to know though that it was not because of errors performing the upgrade. Thanks again...

John