When discourse composes a summary email for a user, does it somehow consider which groups that user is a member of? If not, wouldn’t that be a nifty (optional) feature to improve the relevance of summary emails?
More specifically, the idea is that if user A is in the same group as users X, Y, and Z, A probably has something in common with X, Y, and Z. So if one or more among X, Y, and Z liked or responded to a topic, chances are that A will also find that topic interesting and it should therefore be included in the summary email for A. In other words, this would imply something like attaching a weight to likes based on group membership.