At the same time we land a patch in bug 1099032 that turns the vertical text pref on, we should make margin-inline-start the real property and -moz-margin-start the alias, etc.

We actually can only do this once we remove the pref, not just flip its default value.

I think we should do it sooner than that; we can just pull the necessary properties out from behind the pref -- such that if we want to turn the pref off, we'd need to back out a (small-ish) patch.

OK, fair enough. The patch won't be tiny, but if we need to back it out it won't be impossible.

I've added dev-doc-need long time ago, but I wonder if this has an effect on Web Devs. We are only swapping properties and their alias. Am I right?

It affects serialization of style rules (e.g., element.style.cssText) and iteration of the properties in a style rule, since those show the canonical form rather than the alias.

Thanks. The old pages (-moz-*) now redirect to the new ones. Also added a comment in https://developer.mozilla.org/en-US/Firefox/Releases/42#CSS

Added the site compatibility doc as well: https://www.fxsitecompat.com/en-US/docs/2015/cssrule-csstext-now-returns-unprefixed-writing-mode-aware-properties/

On Firefox 41, the Page Inspector was also showing the prefixed properties rather than unprefixed ones. I was confused myself while working on Bug 1208123. Will update the compat doc ;)