This is evidently as designed (see http://trac.webkit.org/browser/trunk/Source/WebCore/editing/Editor.cpp#L1168 ) However, this is somehow un-windowsy to beep in this context, I know of no other Windows program that does that. There is a bug report in Chromium to change this behaviour (http://code.google.com/p/chromium/issues/detail?id=36963) so we would like to alter it at least in the Chromium specialization.
Would be probably fine to do it this for all ports on Windows. CC'ing some Apple folks who are likely to have an opinion on this. One comment in the chromium bug suggests that this behavior may be seen as superior even on Windows, even if non-standard.
Commit - https://chromium.googlesource.com/chromium/blink/+/6922aa43091479121d91b9c48202925002fc6e76
So Chromium stopped doing this even on macOS? Doesn't look like Mac platform conventions were considered by Chromium authors at all - there wasn't even any discussion of that in the PR. In any case, the Windows port is gone, so there is nothing for us to do here.