I don’t think there is much you can do aside from puttting the information in the description - if people are unwilling to read, they are unwilling to read and there isn’t much to be done.
Personally I’d like to see the original posters vote count as more for defining captivity, but that could have possible undesirable effects - i’ve had people mark clear zoo animals as ‘Wild’ in response to me setting them as captive.
I have posted several observations of wild-caught animals that I did not get to photograph until i brought it back to the lab (especially true of microscopic organisms), and have encountered argument to the effect that if they are captive at the time of the photo being taken, they should be marked captive.
Hopefully you get a reputation with the local identifiers to you who can help correct mistakes suggested by passers-by. If there is a project set-up for identifications in your local area, consider joining it and making yourself known.