Thomceit Positivity Moment!
I do think the "he's against Nazi's" line, while clearly meant for humor, is super important to their relationship. Just the fact that, because of his upbringing, Thomas feels at every turn that he has to justify and fight to include Janus, and when he feels there isn't an in, he makes one. Because he really just wants to listen.
I just. What if there was someone who loved you so much they were willing to be the villain so you could feel like you still loved yourself.
Alternatively. What if there was a person who was the manifestation of everything you thought made you a terrible person, but you still made an effort to care for them and include them because it's so much easier than trying to love yourself.
They're kind of the best metaphor for self love maybe ever?
Come to think of it they're also just a great metaphor for a regular relationship. We have different ideals, and we want different things, but fundamentally we are working towards the same goal, a vision where both of us are happy.
The fact that Thomas is the only one we've seen Janus genuinely be silly around. (Always remember, "you're just stuck with a snake boi" was said when no one else was around) Like he feels like he needs to keep up appearances around the other sides but for Thomas? He can just be himself. Because Thomas IS himself.
Just the fact that Thomas has never had to defend himself against Janus or like been told by Janus that he needs to change. All of Janus' schemes have involved Thomas or one of the other sides making the ultimate decision. Because while Janus does think his vision is the best vision for Thomas, he recognizes Thomas for the whole of who he is, and that he is so much more complex than Janus can understand.
Miscellaneous Head canons:
Thomas is the only one of the sides who emits actual warmth because he's. Y'know real. So Janus enjoys cuddling up next to him.
Though Thomas may not be the best at figuring out if Janus is lying, he can read his gaze like a book and they have a lot of non-verbal communication methods.
Whenever Thomas gets himself an extra treat or takes a little too long in the shower or says no to an exhausting favor he whispers "thanks Janus" to himself and Janus never responds but they both know he heard him
Thanks to @misspelled-magic for this request! It got buried in my activity feed a bit ago but here it is!
Send me a pairing and I'll tell you what I love about them!