If you are receiving unwanted Instant Messages from a single person, you can click on the Ignore messages from (member name) link at the bottom of each gram. This will tell you that "Messages from (member name) will no longer be delivered." This will stay in effect until you click on their name in the panel again, as if you were going to send them an Instant Message. You will get a box that says "You are ignoring (member name). Do you wish to revoke the ignore?" If you choose Yes, then messages will be delivered as normal again.
If you feel intervention is warranted, contact an Agent or a Publisher if one is on. If neither is available, contact an Editor or Genie. If for some reason there is no staff online, leave a message for Wyatt Earp.
Thanks to Khaliq al Marid for the above portion...
Personally, I say forward ALL questionable grams via "Copy for Admin" (located at the top of you gram) and then hit ignore to those who are pests.
Best of both worlds.

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