Yeah, Helepolis was one of the much more known members in the older boards. It was also during a time when MotK was much more active and was one of the pillars of the Touhou community in the West, so if you were popular here, chances are you were also popular/influential in the Western Touhou Community as well.
Besides the comic with Warugaki where they met up together (with Helepolis in cosplay), he was known for being the Remilia guy and liked to play around with his CHARISMATIC RED font sometimes, and he was extremely helpful with the community, but also created a lot of discussions and helped out with events like the Idiot contests (back when we had a strawberriespost board). I know he's not really around here anymore but he was a huge part of my life in MotK back then.
So to answer your question, yeah he was that popular.