I'll tell you a secret...
All right it isn't a secret really, but I saw Brett or Zac (official Frontier staff) say in a support question that you can see if someone is a CHC member by looking at the background of their posts (the black background behind the text).
There is nothing but black/grey if you don't own the game/CHC/Early Bird.
There is a standard Planet Coaster logo if you own the standard game only.
There is a slightly golden Planet Coaster logo with a sort of smile in it (like the t-shirt) if you own the CHC membership. I only don't know if this will be the same for Early Bird owners and Early Bird owners that do not own CHC membership.
You can see this when viewing the forum on the standard theme, not on the mobile theme.
[praise]