Diamondman is the forum nickname of a man Artemis used to work with. Not long after she started that job, she was chatting with a colleague in the coffee room about jewellery, when Diamondman asked her if she didn't have anyone to buy her diamonds. She asked the forum if this might be a subtle way of him finding out if she was single and that started a thread which ran to over 180 pages and encompassed forumites wearing wedding dresses and Artemis-masks hiding in washing machines, copies of flirtatious emails and texts between the two, pictures of Wallace and Grommit, and ended in forum fury when he turned out to be engaged to another. Diamondman left that job last year but the forum still thinks of him and of what might have been wistfully.
Many thanks to Artemis for supplying information on Diamondman.