That blue pentagon icon
 

On the summary screen for a Pokémon, there's a strange blue pentagon next to the markings. Does anyone have any idea what it means? I haven't seen a single Pokémon without it yet.

One thing I do know about it is that Eggs don't have it.

To clarify, eggs themselves don't, but the Pokémon that hatch from them do.

I've been searching all around but it's generally... unknown.

Theories are that it could mean that the Pokemon passed a legitimacy test; or that, since Kalos's shape is the pentagon, that the Pokemon was caught/bred in Kalos. I haven't chosen to go with one of those theories, Janus isn't with me today.

Hm, maybe, specifically, it's a region identifier? We won't be able to know for sure until the Pokémon Bank comes out, though.

Looks like we now know the meaning of the pentagon icon now. It's there for Pokémon who have passed legitimacy checks and came from something within XY.

I'm pretty excited about this. Game Freak seems fairly confident in their abilities to rid Pokémon of some of the more troubling hacks, and I just hope their product reflects what their confidence is telling me. Hacks bug me. Good ones don't. Absurdly impossible ones too. Exciting stuff so far!

Incidentally, I think old Pokémon seems to be useful for Pokédex purposes only as they can't be used in official tournaments.

Ahh, Pokémon that are from previous games are not allowed in tournaments?

(Note to self: consider doing the same for tournaments here.)

Uh huh. Seems like this is as close as a clean break, third-gen style as possible without actually cutting off compatibility.

Hm, I'm betting a lot of legitimate players are cursing at that kind of news, particularly ones who have competitively training Pokémon for a few years. I will comment that Game Freak is quite devious, as I remember my previous thoughts: will there be a method to transfer Pokémon to Gen VI, or will they want to keep the games clean and start anew? 'Course, I'm guessing bred Pokémon will have the pentagon. If not, there goes Typhlosion.

They managed to choose both, eh?

Hopefully, that is the case. If the games check for legitimacy of the parents and decide to never give any children the seal of approval if any parent doesn't have the "passed legitimacy" seal of approval... yelp!

Not that I don't believe you, but can I have a source on this? I for one actually support a move like this to make it so that pre-VI pokemon have their movepools reset to the VI standard as well as RNG'd pokemon now have no gravity once more.

Yeah, I didn't see anything about them not being allowed in competitive play. I thought that was only speculation. I really hope it's true though. And I'm almost 110% sure that the babies of great competitive Pokémon will get the seal of approval. They'll be born in Kalos under the Kalosian breeding standards, so I don't see why not. It's much like how breeding two hacked Pokémon will result in a perfectly legal and legit Pokémon. But... I'm worried that the pentagon will be an easy addition to code into whichever Pokémon you want... I sure hope not!

Speaking of being usable, well... I've been keeping track of Serebii's updates (Get to Friday 15-11-2013 GMT).

To quote the specific part of the source, as things fly off the homepage pretty quickly:
Anyway, I didn't think about the moves. That does indeed limit a lot of Pokémon. What will become of move tutors, though? How many of the moves can still be passed on as egg moves?

I think I now also know why Eggs don't have that mark.

They have missing information!

Looks like there's confirmation that the pentagon indeed means that the Pokémon was created within Pokémon X/Y.

I don't know about this. I like the concept, but I hope it's more of a stat-checking thing. Cloned Pokemon are much easier to trade for and therefore allow more people to get into the Metagame. I personally wouldn't mind clones. If it were something like 700 Base Attack/Speed, that's a different story.

It is a stat-checking thing in a way. Pokémon with this mark are know to originate from Pokémon X or Y, and have legal stats and moves. Clones would also have the mark... seeing as they're essentially identical. Cloning in XY is still an extremely risky affair, so it shouldn't be too common.

Base stat changes are based on the game data itself, so it's something that you won't have to worry about.