Given when Elliot would logically be talking about, it's unlikely Tedd brought up anything related to gender (or, if Tedd did, elaborate justifications were given).

It's safe to assume that, by this point, Elliot has heard such ideas from Tedd.

Labeled Balloon

Elliot was the last one shown talking, and I thought it would take half the speech bubble to get a definite "Susan" vibe, so I unleashed that "S" in Panel three to help identify Susan. I felt having those identifiers throughout the storyline would have been overkill while making the panels look more cluttered, but it seemed like a good idea here.

And yes, that crossover was definitely with Justin. At least, that's authorial intent. If you want to assume it was with anyone else, I can't stop you.

I'll try, of course. There'll be a fight of it! But, in the end, you'll win. Such is the way of subjective interpretation in the absence of definitive canon confirmed within the text itself (and sometimes even when it is confirmed in the text itself).