Thanks bluewho, I don't think what you say is nonsense at all. I wanted to make the same point and have wondered about Dan's gender identity myself, but don't think there is really enough information out there to say much and don't think the behavior that @lefthandedism
mentions is necessarily indicative of Dan expressing a transgender self.
(Disclaimer: the following criticism is not aimed at you personally @lefthandedism
and is not restricted to your post but more of a comment on things I've seen written around Dan's gender within the fandom at large )
The problem I see with bringing up nail polish, (rather cliché) female characters in sketches (I miss them so much
) and Dan wearing dresses in support of any claims about his gender identity, is that they only really mean something if you start from a very gendered view of these behaviors. If one says "interesting he seems to be comfortable wearing nail polish" and connects that behavior with gender, it's implied that nail polish is a marker of (identifying as) that gender. Otherwise why bring it up in that context?
This is exactly what some guys and girls are brought up to believe: nail polish is for girls. People in the fandom don't intend to police his gender but in using this to make claims about his identity they ironically enforce the idea of nail polish being "not for straight cis guys.". One is essentially relying on the validity of a stereotype to argue "hey look Dan doesn't conform to this stereotype this must mean something!".
Apart from that more principled objection, I think we should also exercise caution in reading to much into relatively infrequent behaviors that might be triggered by a specific social context. In the case of nail polish, there were multiple people at different occasions suggesting they try it, and libraries full of tweets expressing immense joy and the hope they would some day do it. So it's very likely they caught wind this is something that some people really would have liked to see and gave the people what they wanted. Much like when they showcased their pastel personalities, I wouldn't assume it's a sign of their true identity.
Wearing that dress also happened within a very specific context. I don't think when some guy youtubers meet up in private they tend to spontaneously undress to their boxers/ wear dresses and start dancing in lines for the audiences' entertainment. This was clearly part of the Stickaid shtick, and while I think it's noble Dan was willing to dance in a dress for charity, I wouldn't think his choice to wear a dress at that occasion reveals some inner desire to express a feminine identity.
Dan is also a bit of theater guy (or at least that seemed to be one of his major hobbies as a teen), and wearing dresses is a bit of an old trick in theater. I've done it myself with a bunch of other guys and it's usually done for comedic effect (and good fun to do). It's got a long history within the art. Men dressing up as women was a mainstay in Elizabethan England, in which it was considered unthinkable that a woman would lower herself to being seen on stage pretending to be another woman in public. That’s was "a man’s job", especially as so many plays contained saucy humor.
I'm not saying any of these medieval beliefs or current traditions inspired Dan when he scripted Becky or Rebecca. We can only guess as to why he chose those characters and depictions. However I also see no reason to suspect an underlying questioning of his gender identity motivating that choice.