The account status (be it active, travelling or inactive) of a user is not made public on the Postcrossing website, the existing “Last login” only indicates last appearance of a user, but cannot be used to distinguish whether it’s from their travelling location or from an inactivated account.
I suggest to append a simple iconography to the end of the displayed username, for example, with “
” denoting travelling, " 
" denoting inactive, etc.
Edit: Unicode character rendered as emoji by default.
As for me, I definitely would not want my status made public: it is no one’s business whether I am traveling or away from home. Also, only active addresses are given out, so marking “active” or “inactive” makes no difference to me in drawing a profile, and the “last login” already tells me if a Postcrosser is active recently or not.
I don’t mean to sound harsh, but I think status really is a private matter.
I agree because it could attract stalkers!
Points taken. Privacy is indeed a big concern that I’ve overlooked. (Maybe an show/hide option could help?)
My original intention was to make it easier to figure out the cause of extended travel times of sent cards (other than the usual problem with postal routes, like delivery during vacation, or worse, deliberate actions). Guess this proposal just isn’t the best possible way.
I apologize for the disturbance.