There appears to be some sort of focus bug when moving focus from an input into an editable iframe. Specifically, when you click in an input and then into an editable iframe, built in editing commands like command + b, command + i, do nothing and we do not receive the key events if we listen for them. Clicking anywhere else outside the iframe fixes this.
This happens if focus is moved via click or via tabbing.
This is only seen in Safari on Mac, not Windows.
This happens for both contentEditable and designMode.
The URL provided show a demo page that exhibits this behavior.
We see this problem in Gmail when the user is moving from the Subject or To line into the body of the email. We had a hacky workaround where we were listening to focus and re-calling focus on the iframe window and then the editable node which did work around this issue, but raised a bunch of other focus related problems and we needed to revert that.