I guess I'll give my feedback here since I haven't done so already.
So I understand that the idea of this reversible tee was to be subtle while still being recognizable to someone as neuro merch. I think this can be pulled off and what we got is, in my opinion, an all right base for more to be added.
As the shirts are now though, it veers too far into subtlety and goes into, in my opinion, being quite generic. Neither side has enough on it to make it look like Neuro merch. The most we have are the cogs with the hearts at the center on neuro's side, but that's it, really. Unless you know this shirt exists, i doubt most people who've heard of Neuro would recognize this as a Neuro/Evil shirt
There's lot of things that I think could be done for this. An extra color for each side would be an easy start, adding blue or yellow for Neuro and a darker red for Evil would probably make them more themed round the twins.
An idea I saw floating around that I am completely on board with is a harpoon going through the broken heart in the back of Evil's side. You could alternatively go with a metal pipe in the middle of that, since it looks more like the heart is shattered than split, in which then you could harpoon the balloons on the front to make the popping work. Neuro's side could have the gymbag drone somewhere, which is an iconic neuro drone design for her, but to aa normie would just be a neat detail.
I also think Neuro's side could have something osu related somewhere, going back to Neuro's roots as well as the roots of the community itself. Could probably put that on the front as circles to press if possible to pull off.
That's just a few ideas I have. I think the fronts of both designs could definitely have more on them while being subtle.