The unveiling of a new Doctor Who costume is a lot like a superhero rebranding -- or a new collection by an established fashion label. It's a combined attempt to get people excited about innovation, while reassuring everyone that not too much has changed. And so, the BBC announced Capaldi's new costume by talking about how it blends elements of old and new -- for example, the visual callback to John Pertwee's costume.
Thanks to the age gap between Capaldi and Matt Smith, the whole "old vs. new" thing is specifically relevant to this regeneration. Smith was dressed in an almost grandfatherly way (tweed, bow tie and braces), but that had the side-effect of making him look like a hipster. This was problematic because the Doctor's costume should never resemble a current fashion trend.
If you can look at the Doctor and say, "That guy looks like he should be hanging out in a vintage shoe shop in 21st century Hackney," then it detracts from his image as an alien -- although of course, if you make him look too alien then you can't take him seriously. Capaldi's costume sidesteps this issue by being extremely simple and pared-down, which I enjoy a great deal (not least because I want to wear the entire outfit myself).
Looking at Clara and the Doctor in the first episode of season 8, the similarities between their two outfits are obvious. He's wearing a white shirt with a prominent collar and no tie, in a more severe version of Clara's lace collar. Then there's the black/white/red color palette, and the fact that he's wearing a cardigan rather than a waistcoat underneath his jacket. If you wanted, you could probably even stretch to linking Clara's tartan skirt to the fact that Twelve has a Scottish accent.
To me, this link between the Doctor and Clara's clothes is a clear sign that intentionally or otherwise, he imprinted on her after regenerating. (Although if you look at Clara's cardigan, you'll see that it's patterned with bow ties -- a callback to Eleven's signature accessory. She's still looking back to the Doctor's previous incarnation, whereas the new Doctor is calling out for her attention.
I no longer have much trust in Steven Moffat as showrunner, but I enjoyed the way the new Doctor was introduced as being rather emotionally vulnerable. He isn't just desperate for attention (which would be typical for the Doctor) but is needy for support from Clara. When he puts on his new costume for the first time, he immediately looks to Clara for reassurance.
Intriguingly, there's a third person in this regeneration costume club: "Missy." This character is almost certainly a villain, and seems to be collecting people who die as a result of the Doctor's actions.
Missy wears a female version of the Doctor's costume: A stiff white collar with no tie, and a black coat with short lapels. Missy is also clearly linked to the Doctor in some way -- although the less said about that, the better. I don't trust Steven Moffat to introduce a female antagonist who refers to the Doctor as her "boyfriend."
Regarding Doctor Who's increasingly dubious relationship with its female characters, I have mixed feelings about Clara's tenure on the show. Her characterization last season was practically nonexistent, but season 8 seems far more promising. Unfortunately, I do have some problems with this new running "joke" where the Doctor makes fun of Clara's appearance, because it's just so... pointless and mean? Moffat is weirdly obsessed with the attractiveness of his female characters, and this often carries over into episodes by other writers.
Moffat may not write every episode, but he's in charge of the overall story arc and tone of the show, which often means editing or adding to other people's scripts. For example, I find it difficult to believe that last season, Neil Gaiman wrote the Doctor describing Clara as “a mystery wrapped in an enigma, squeezed into a skirt that’s a little too tight." This line obviously annoyed me due to Moffat's history with female characters, but also because Clara's skirt was not actually tight during this scene. If you're gonna insert creepy, sexist comments into the show, then at least make sure they're relevant.
When you combine this with the way Moffat talks about women in real life, all those comments about Clara's appearance are far more distracting. In two episodes, the Doctor has called her "short and mannish," mocked her (supposed) vanity, said that she was "built like a man," and commented that she looked tired and it was good that she was "still making an effort."
The thing is, all these jokes seem to have come out of nowhere. In "Deep Breath," the Doctor says Clara is egocentric and obsessed with her appearance, but we've never seen much evidence of that. Not unless you count the fact that she always has nice hair and clothes, which you could equally have said about Martha back in season 3. Then there's all the unrelated comments about her appearance from characters like Strax, which are apparently just included for laughs.
If this dynamic only existed between Twelve and Clara, then I might accept it as a quirk of their relationship. However, we've already seen plenty of Moffat-era episodes that include things like River advising Amy, "Never let the Doctor see you age." Moffat has a creepy fixation with gender roles and women's looks, and this is inadvertently ruining a characterization detail he introduced in "Deep Breath": Clara's vanity.
I really enjoy the idea of Clara being a little vain about her looks, because it's very rare to see this trait in a "good" female character. It also explains why Clara always looks so pretty all the time, because otherwise we'd have to assume that it's simply because she's a young woman on TV. Sadly, this characteristic is completely undermined if we only ever hear about it in the context of male characters mocking and belittling her for it.
Modern Doctor Who has been very good at providing realistic costumes for its female leads. Rose's hair, makeup and fashion sense all looked appropriate for a 19-year-old girl who grew up in a London council estate. Donna wore clothes that implied she shopped in bog-standard department stores, while Martha, a doctor from a more middle-class family, looked a bit more put-together. Then once we reach the Moffat era, both of Amy's jobs ("kissogram" and fashion model) were based on her attractiveness, so her casual-but-beautiful appearance made sense. But Clara's fashion sense was always a lot harder to pin down, partly because the show failed to tell us much about her as a person.
Compared to the family backstory for Rose or Donna, Clara's background is virtually nonexistent, which didn't help when combined with her shaky characterization in season 7. In her first episode, "Clara Oswald" is actually Oswin the Dalek, who is portrayed by Jenna Coleman in a sexy red dress, perfect makeup and an apron (because she loves to bake). Clara's "real" appearance is a little more toned-down, but is still very pretty and feminine.
In the second episode of the new season, one character remarks that Clara looks like a schoolteacher -- which she is. However, those schoolteacher outfits (patterned dresses, cardigans and cute accessories) alway look very fashionable, which is why I like the idea of Clara taking a lot of pride in her appearance. It explains why she always has such perfect makeup, shiny hair, and great outfits, and I like the idea of a female character who can be heroic and nice, but also kind of vain.
It's just too bad that these traits are accompanied by the Doctor making cracks about her appearance, since this show already includes way too much gender-based humour.