Well, the MTF-accounts of big three have been a well-protected secret up to now, but somehow the information has leaked:
Rafa's account: swiss_tennisgod.
This may come as a surprise. For years Swiss_tennisgod has entertained us with rants of epic proportion whenever Federer has encountered devastating losses. Perhaps he has expressed his despair even more eloquently when Federer's Spanish rival has secured important victories. Some may question the above revelation, but Rafa's sense of humor is underappreciated. Perhaps someone will claim this cannot be correct, arguing along the lines "no way this be true, Rafa's English not good enough, no". This objection might have some merit, I guess, but it is simple enough for Rafa to write in Spanish and have someone translating it.
Federer's account: Darth Vaderer.
Originally, Darth Vaderer claimed to be a fan of Federer (maybe he still does?), but whenever he makes a post, the bottom line is always that Federer doesn't hold a candle, neither to Nole nor to Rafa. Darth Vaderer has sometimes claimed to possess intel from sources being close to Federer. To make sure his real identity is not revealed, cleverly he makes sure his predictions are always wrong in such cases. We can only speculate on the reasons Federer has to roast himself. I sure don't know, but maybe it gives him an ego boost when his troll account (almost) wins the ACC contest. Or perhaps the Swiss legend just have an odd sense of humor.
Nole's account: Meddy bär.
Meddy bär comes across as a friendly guy with a sense of humor. He is also a rather clear supporter of Thiem (in addition to the "bullshit Russian"), but this is just a cover since he posts under the Austrian flag. To further hide his real identity, Meddy bär sometimes comment on matches taking place when he plays himself. In this case, Nole's brother Marko is the one using the account. Even though Nole has taken extensive measures not to reveal his identity on MTF, sometimes the influence from Pepe Imaz can be seen, particularly when "Meddy bär" occasionally hits the like button on posts he does not really appreciate.
@Henrik, appreciate the analysis and I have long suspected of Darth Vaderer too, based on supposed intel from close sources as you suggest, but between him and Theseth it has to be Theseth!
He's the one calling Federer Rogie all the time (intimacy), and keeps opening threads like "when will Rogie win this an that"; no way I believe can Rogie keep his "cool as a cucumber" act about his records being threatened by the other 2