Is there any kind of output in the browser's error console when you try?

Hm, how do I find the browser's error console? If it's F12 and Console, then no, no messages there.

I noticed that if the page I was editing is not scrolled to the top, when I try to paste, it behaves as if I press arrow up.

eliashedberg wrote:

I had the same (or a similar) problem in Chrome 29.0.1547.62 under Mac OS X 10.6.8: when pasting the string "Lavoslav Ružička" into the edit summary the page behind the summary jumped down and back up (or the other way around) but there was no text inserted into the edit summary.

I can recreate the failed paste action in the edit summary of my sandbox, but the text behind the edit summary doesn’t move (potentially because that article is too short).

I can recreate the failed paste action with other strings too (in Chrome), i.e. no pasting works, no matter what string I try to paste.

In Firefox, pasting into the edit summary works fine (Firefox 23.0.1, also under OS X 10.6.8).

I'm observing the exact same problem in the same Chromium version on Ubuntu 13.04 (no error messages in the JavaScript console, works fine in Firefox).

en.wp user ToE reports:
[this bug] also applies to Google Chrome, version "29.0.1547.66 (Official Build 220848) m", JavaScript V8 3.19.18.19, running on Windows 7 Home Premium, Service Pack 1. Paste into edit summary works fine on the same machine in Firefox version 23.0.1.

en.wp user ToE further reports:
Upon upgrading to Google Chrome: 29.0.1547.76 (Official Build 223446) m, JavaScript V8 3.19.18.23, paste into edit summary works properly.

Now that the edit summary is in its own window, this bug has gone away. I don't know whether the plan is to eventually return to the edit confirmation flyout - if so this bug may well reappear.