What you are doing is a bit of a grey area really
Publicly naming and shaming is strictly against community guidelines
Letting a screenshot do that for you while strictly speaking may not be the same thing could be considered close enough if your topic gets enough attention to warrant punishing you
Here:
“Accusing named or otherwise identified individuals, guilds, etc. of dishonourable behaviour, such as cheating or “ninja looting”, will lead to post/thread deletion and a suspension. While such warnings may sometimes be warranted, allowing targeting of others in such a fashion is open to abuse and thus not allowed. You may present your point of view while preserving the anonymity of those involved, and let the reader decide whether to contact you for details”
Read more about community guidelines here