1. How does the feature work? When a user toggles their editor to use BBCode, the editor will remember that decision so that the next time that user posts it will start them in BBCode editing mode. In other words, exactly like it works on the current forum.
2. Does an example of this feature exist on any other forum? The current version of Minecraft Forum does this.
3. What value would this feature provide to yourself and others? Some users, like myself, prefer to have tight control over the formatting of their posts and prefer this over the ease of use that the WYSIWYG editor provides. It will also be useful in the unlikely event that the new forum someday experiences a similar bug to the current one where in editing in the visual editor risks post corruption.