Currently replies people I follow make that only tag people I do not follow, whether that is one or several people are hidden from my home timeline which I believe to be an important feature.
Currently mentions (i.e. the first toot of a conversation) from people I follow that only tag people I do not follow -do- appear in my home timeline.
This is both A) a personal discomfort but probably more relevantly B) I don’t see a meaningful difference between these two scenarios and don’t see why there are different rules for how they are presented to me to the point I initially took this for a bug.
I would propose that these two types of toots should be identical in function, a mention should just be considered a reply to a toot that doesn’t exist.