I just don't get why so many people are assuming she's some Time Lord or other. A Time Lord's regenerations are played by different actors, not the same one.
It's as good a theory as any other, but the Doctor would've sensed it if she were a Time Lord, so it's an easy theory to shoot down.
Jenny had still recently been created. The new show has suggested a certain lingering regeneration energy that heals you without transformation early on in the process. If Clara starts shooting electricity from her fingertips, the Master argument will have more merit. Assuming she's a Time Lord regenerating would mean that we witnessed her final death, because you aren't regenerating from being turned into a Dalek. I doubt they'll do that twice. The whole arc would directly parallel River.
It really isn't Moffat's style to just spring out old villains as twists, that was more the style of the previous era. Clara will be something new. And hopefully not too underwhelming because I like her so far. I think? Judging by her 2 copies or whatever.
Maybe she was a stowaway or a kitchen hand on Skagra's ship at the beginning of time and she was split into 12 duplicates across time space too when it exploded? Good lord! She better not be the key to fucking time!
I cant help but wonder that if there is indeed versions of her splintered in time, it might not be a good idea for the Doctor to start taking one version on a journey though time, it may not end well. of course if a new version is not created until the previous one dies it might not be a problem, just something to consider.
What defines a rare exception? The Doctor's regenerations have been all over the place. Otherwise we just have Jenny, Romana, The Master, River, and that one guy who was hanging with his next incarnation. Also, with the fob thing, how do we know what happens when they die in that state? If the rule is a new body, how do you account for those who seem to be able to determine their new form? Romana chose to look exactly like Astra. The Time Lords offered the 2nd Doctor various choices. Who's to say that couldn't be the same one?
Do you think you can regenerate from turning into a Dalek? Do you think you can regenerate by teleporting to an entirely different location (keeping in mind Clara was buried). There have been subtle variations in regeneration over the years, but nothing as big as those things.
What you're doing is starting with a desired conclusion and constructing arguments to justify it. That's backward reasoning, because you can use it to support any position, no matter how wrong or nonsensical. Better to reserve judgment until we have more evidence, then formulate a hypothesis based on the evidence.
On watching the episode again, I think it was possibly foreshadowing a return by the Great Intelligence later in the season, but not foreshadowing some kind of Doctor memory-loss thing. If it is a setup for a future GI story, then it makes sense not to give away too much now -- hence the noncommittal "rings a bell."
"Rings a bell" is a reference to the fact that The Abominable Snowmen has the Doctor get involved with the Intelligence and the Yeti when he tries to return a ghanta - a *bell* - to the Det-sen monastery, of which the Abbot Padmasambhava has been possessed by the Intelligence...