...And apparently, still doesn't, going as far as making fun of a black belt for teaching kids, only to get choked out by said black belt in the second round and rolling over and giving up his back.
I really don't know if he's a legit brown belt. Having trained and come up in a tough(er) gym environment, I'm usually not one to ever say who's legit and who's not, but at this point, I've seen plenty of footage of him grappling in training. Quite frankly, I go to a little hole in the wall school in downtown Toronto that is a Carlson gracie affiliate. We have a really awesome lineage of really serious bjj players, but we have no champions or even really too many serious competition guys, just a few. but again, from what I've seen at this point, I've become pretty convinced that the few brown belts at my school would turn McGregor inside out.
it's one thing to know and understand the techniques and be technically able to perform them. It's quite another to maintain that skill level through an actual fight/competition (whether there is striking involved or not). Lot of people have talked about how good he is; obviously coach Kavanagh has been talking him up, even saying that he "wouldn't be surprised if McGregor submits aldo" because he's "given hell to every black belt in the gym" (didn't know there were multiple black belts to give hell to over at SBG...gunni is a BB but are there others?). Eddie bravo has also talked him up, but more focused on his dedication to training as a good sign that he will eventually one day be very good.
the only things we've actually SEEN though, are McGregor losing in the first match to a purple belt back in 2012 ( http://www.mmafighting.com/2015/7/11/8401077/kywan-gracie-behring-the-last-man-to-beat-the-notorious-breaks-down ) and then of course, getting wrestlefucked by mendes for a couple minutes and then, of course, exposing his back and flattening out to get choked by Nate. I don't know if he's entered any serious BJJ/grappling competitions since the loss in 2012, but he really should think about it. a single BJJ tournament is worth 3 months in the gym in terms of experience and growth. Mcgregor NEEDS to clean up this part of his game, and, barring becoming a serious jiujitsu player, at least focus on getting a few high percentage subs under his belt, and just train exclusively on a get-up/sweep game that puts him in position to seek those high percentage subs.
I've searched around a bit and I can't find any mention of him doing any BJJ competitions except the one linked. maybe it's time for him to get in there, do a few more and see where his ground game is really at, regardless of belt colour.