The two main categories for advanced following preferences are "All Messages" and "Following Only." Under "Following Only" is a subcategory, "First Message Also." Following Only is indicated in the member list (and the member's group list) by "F," and "First Message Also" by "FF."
There is another classification, "Auto-Follow Replies," indicated by "R," that I think may be both misrepresented and misapplied.
"All Messages" says "Every message is emailed to you, according to your Email Delivery Selection, except threads or hashtags you've muted." So if a member is subscribed via All Messages, rather than Following Only, and they just click on "R," it's not clear that R does anything - unless it is meant to undo any muting that the member has selected?
If the R restricts their deliveries to topics within which they've replied, then R should be a subcategory under "Following Only," just like "First Message Also." The members in our group with just "R" are receiving all messages - not just the threads in which they reply. At minimum, this is probably confusing to them and they probably don't realize why the "R" isn't doing anything (i.e., they're still receiving every message).
OTOH, if "R" can be legitimately selected without also clicking "F" (because, rather than filter messages, it overrides muted threads and tags), then it seems that "FF" should likewise be selectable without clicking "F." And it is not - it is a subcategory under "F."
So bottom line, I think that either both R and FF should be subcategories under F, or both should not be; and in the latter case, their function (overriding mutes) should be better explained.
Messages are the sole opinion of the author, especially the fishy ones.