For my twopenneth I support keeping the road and mountain sites together. I have both, I ride both and I restore both. I even, heaven forbid, ride my mtb on the road and I have a (fairly) modern hybrid which is a general purpose bit of both....
But mostly it would be a real shame to lose access to the knowledge of all the people who rode, sold and built the bikes we now describe as retro and who have been kind enough to provide me, and lots of others, with their wisdom and in my case lots of essential help since I joined.
This site has two unique features - it specializes in older bikes and it has a broad technical base - which attracted me in the first place.
In case you are in any doubt I am not in favour of a split....
Claud Butler Carabo, Marin Muirwoods, Giant Cyprus SX, 1958 Carlton, 1982 Colnago,