They are playing and someone ghosts to them in admin chat accidentally IE _____ to admins: My traitor buddy _____ RDMd me
Depending on the severity it would differ. Staff are allowed to play as a regular player as well, and normally if we run into this(which we often do on Vanilla servers) we'll politely inform them how to adequately inform a staff member of potential RDM in the future. This teaching also serves as a warning and normally includes a stated one as well. We will kill ourself if we are not a Traitor and sit the round out. It's part of the sacrifice we make to ensure our players have an assurance of fair quality gameplay. It's affected by situational factors none-the-less(I.e Player history).
It is not ghosting since the player is coming to you about a staff related matter. You kill youself in this case and then handle it like you would a report. Staff are instructed to not consider this ghosting, and there may be something in the extended rules as well.
https://www.seriousgmod.com/threads/a-guide-to-sgm-extended-rules.12605/#post-109984 That statement would lead me to believe that your example would qualify as ghosting. However, in practice, accidental ghosting in admin chat is treated as mentioned above. That being said, I have observed cases where users maliciously use admin chat even though they have been explained the correct methods. Those players do end up getting a ban, as it is intentional.
If I may, even if Im not staff, I have asked a question like this to Mods/Admins who were online at the servers. What I have been told is that you shouldnt message a staffmember who is alive, about who is the last afk Traitor or anything at all that reveals a player as inno or Traitor. Wait till the staffmember/s are all dead, else you would be ghosting to the staffmember/s. And considering the situation where a Traitor RDMed his T buddy, well this player who got RDMed have no need to Tell anyone that " ___, My T buddy RDMed me" All they need to do is file a report and let the satff take care of the rest o.o So sharing that information, when all you have to do is report the player for RDM, is unneccesary and in my opinion, would simply be ghosting o.o Keep in mind this is just my opinion on this topic, I have no staff right to answer this question ^^