I am fairly sure that there is exactly one person on this site who can answer the MERP question i just posted, due to it being about a fairly obscure game system. Is there any way to get in touch with that user specifically?
1. Leave a comment on any of their posts.
This will give them a little notification in their Inbox and, if your comment is sufficiently well-crafted, may motivate them to help you. A particularly useful comment to leave would be one requesting that person join you in chat.
2. "ping" them in a chat room.
If that user's been in a chat room recently you can "ping" them by addressing them directly in a message. Type
@ and the beginning of their username--if it autocompletes then that user's been in the room recently enough to be "pingable."