According to the Impostors documentation: "You should notice that the "Features" of the avatar now includes "Impostor", except that unfortunately I don't have the feature indicated on VRChat.
I've always had this problem: the day the Impostors came out, I created them on the site. Although the site told me that the Impostors were OK, VRChat wouldn't tell me.
Today, I re-uploaded the same avatar, this time with a new ID, also on PC and Quest, and I have the same problem... even though people can see the Impostors.
Thank you,