User blog comment:Rappy 4187/Technical Update: February 5, 2013/@comment-452-20130205180732/@comment-452-20130206140120

PedroM, you apparently joined in April 2012 - after the new editor was introduced, so you're missing some information.

The previous editor had the category module enabled when the RTE was disabled (with the option to disable it, obviously). They removed this functionality when the new editor was introduced, and it has taken them a over year to restore it. (Although I re-enabled it with javascript a while ago anyway - showing that there was never an issue, it was just arbitrarily disabled.)

Today's change has simply restored how it used to be. Therefore there must have been something that needed fixing.

(Note: I'm uncertain about the exact length of time, trying to look it up now, but it has been over a year since the new editor became available. Edit: multiple people were complaining about it being removed in September 2011 - here's my comment)