(Includes discussion of events through two episodes ago, but nothing specific about last week.)
Is this the season of Jeff and Annie? The musical number in the premiere (which was, of course, happening in Jeff's head) suggested that it might be, and their conversation in the Model U.N. episode made it clear that that's how they're thinking - but also that they realize it's kind of weird and icky. And Community fans seem quite divided over whether the ickiness outweighs everything else, whether the show should even go there at all.
First, about that ick factor: yes, he's significantly older than she is and has a lot more life experience. The show often codes him as an adult and her as a child. To some extent, though, I think both Jeff's cynical world-weariness and Annie's determined naivete are personas they put on to preserve certain images and protect themselves. And by the standards of TV relationships viewers are asked to accept and often root for, this is nothing. She's well past the age of consent and he's not her teacher or her boss. Neither of them are running around killing people or hurting each other. Sure, one or both might come out of this with a broken heart, but come on, this is college. That's what's supposed to happen.
For me, the potential ickiness is outweighed by the reasons why their relationship seems natural and the ways that they actually seem to be good for each other. Again, this is college, and Jeff is exactly the guy a girl like Annie would go for. (And really, under everything, Jeff is a pretty decent person, so Annie could do much worse for her "bad boy" phase.) Other than perhaps Abed, they're the most intellectual of the group, so the pairing is natural from that standpoint. Sure, Jeff is presented as a slacker and cheat, but don't forget that on another show, this same basic character would be - and is, actually, hi Suits! - presented as a brilliant boy wonder who used his innate talents to con his way into a prestigious career.
But most importantly, they seem to actually care about each other and be good for each other. When Jeff is with Britta, she feeds into his cynicism and they fall into a spiral of negativity, but Annie calls Jeff on his nonsense and makes him admit that a lot of the cynicism is an act. And Jeff protects Annie to an extent but also makes her engage with the real world. They see through each others' acts, which allows them to relate in a more genuine way with each other than with almost anyone else. And really, that alone is reason enough for the show to give this relationship a try.