Earlier quoted context omitted.
In these cases you'd have to freeze the version of every layer beneath the editor(browser/env, OS and so on), otherwise any regression in these layers is going to break your app. But if you decide to freeze you run the risk of exposing your users to security issues.
I doubt this? contenteditable is pretty stable in Chrome/WebKit.
Anyway we had our share of trouble with a customer due to an exotic rendering issue that occurred in two consecutive versions of Chrome and then disappeared, so yeah.