XC, others,
This is not a Thyiad post, but it is my attempt at being clear and accurate.
RRM is (afaik) technically allowed in 1.07, but no one (well..) uses it, because "no one" is interested in it. The reason for this is the trading pool, where no one wants to start playing a version [1.07 SC RRM] that essentially no one plays (the vast vast majority of SPTF players are [1.07 SC Vanilla], not [1.07 SC RRM]). As far as I know (probably incomplete information), exactly zero people have voluntarily placed themselves in the [1.07 SC RRM, 1.13d SC FAM] category, where zero (afaik) other people reside, and where they would be able to trade with ~no one else.
ETA: In conclusion, if you want to be able to trade with the community in general, I super super recommend you to stay [1.07 SC Vanilla], like everyone else in the trading pool (except uiniu? His language is (arguably, deliberately) super unclear, and you might want to take extra care to stay in the general [1.07 SC Vanilla] trading pool.