I guess you use your flist in a different way, that's all.
Yup.

to you, it's "dependent on their interest", to you, communication is not just a plus, but the purpose of a flist (Am I right?).
Partly - again, there are journals I have friended that I don't interact with (or all interaction only happens on their turf). So, definitely, but not exclusively.

I think this problem could be solved by establishing reading lists alongside the flists, but I guess that would just be too much of a bother.
My f-list is my reading list, though :oP ! And as far as splitting them up into "people I interact with" and "people I don't interact with, but whose entries I don't want to miss", it wouldn't add any people to either - it'd be the same people as now, just split into two.

I would love the option to browse my fo-list, though, but I can see how in practical terms it'd create two tiers of f-lists, and omg, the wank that could come of that!