Marsh used to post on this forum regularly. I engaged with him a number of times. He got offended by something and left. I think it was a forum rule. I'm not so sure that he has passed on. An internet search for "Anthony Marsh Somerville Massachusetts" finds an unmarried 79 year old Anthony Marsh.
I'm guessing that would be about Tony's age. Maybe he stopped posting because it was too difficult for him to continue posting. Writing about the JFKA seemed like it was a big part of his life so if he quit cold turkey, it must have been because it had become such a chore for him.
Golf used to be an important part of my life but I have hardly played at all this year because I completely lost my golf swing. It wasn't even fun to play. I tried to work it out at the practice range without result. I've learned I can live without golf. I've found out that Jack Nicklaus hardly plays anymore either, but he's 86 years old now.
Getting back to Tony, I first came across him back on the old Prodigy service in the early 1990s. He joined that discussion group shortly after I had. He was very much a CT back then but hadn't become as combative as he did in later years.
UPDATE: I did the same type of search and in addition to the one you got, I got two other hits for Somerville. One listed Anthony C Marsh (age 100+, possibly deceased). Probably not the same guy. Another listed Anthonie C Marsh, age 71. The first name is spelled differently but lists an aka Anthony Marsh so that's also a possibility. For some reason, "C" seems like it might be the correct middle initial. Maybe he used his middle initial on the old Prodigy service. In any case, it's very possible Tony is still around and just not posting for some reason.