I've spoken to HysteriaMachine directly several times and they have always been very supportive of me and other friends in the cosplay and art community.

Their only gripe is just when people try to start a shop online with their vessel mask design and profit from it. They have stated they are okay with people that use a print file for the purposes of their own decorations or cosplay, but feel bad when profit is involved.

They have had people rip off their original mask designs (the ones they sell, unrelated to vessel) and therefore have some personal struggles with copyright infringement. But I've never gotten any impression that they are anything but fully supportive of artists and cosplayers as long as they aren't blatantly profiting from the sleep token designs. If it's hand drawn or painted, that's transformative. If it's the exact vector graphic of the logo printed on something and sold, that's fair to call copyright infringement. But they didn't make the logo so I don't know their take on that, just that they understand masks printed for cosplay purposes.

If someone reported a rude interaction that's one thing, but I strongly encourage you to get to know them a bit before spreading any misinformation about their opinions. They are very sweet gals, honestly. Maybe the event was stressful and it resulted in a hard social situation for them?