I don't subscribe to any surname feeds because I don't see this as a very efficient way to follow editing activity that might interest me. Some of my family names (such as Smith and Clark) are much too numerous to make a surname feed useful; others have so many variant spellings that I could quickly fill my surname quota with just a few family names. Instead, I use my quota to follow 20 topical tags in G2G.
What I would find useful (and possibly what Mark is seeking) is the ability for members to have customized monitoring -- within WikiTree -- of editing activity on profiles of interest, similar to the Family Activity Feed, but without being signed up as a Trusted List member or Profile Manager. I believe this is feasible with the technology, but new apps would be needed to make it happen.