The visual editor, most (if not all) who have it, has a "turn on" or "off" button ... that simple. Who doesn't, doesn't use ... who wants, uses ... the important thing is to have the option where the Administrator defines what will be the default.
About friendly urls, it's almost a consensus, isn't it? The vast majority think this would be helpful.
About features "by extension", I think that's fine for the visual editor only. But for the friendly urls, it is not advisable, as the developer may suddenly stop following it and each new version of the forum will stop working, breaking the whole URL system and detonating SEO.
EN: Do to others what you would want them to do to you.
ES: Haz a los demás todo lo que quieras que te hagan a ti.
PT: Faça aos outros o que você gostaria que fizessem a você.