The reasons for the difference as pointed out by the parent comment are valid and are what is making the interactions different, but I think it might not be "fundamentally". I can also choose which comments I respond to, which conversations to interject in, although it is a markedly different and easier experience to do so - online it's as easy as closing the tab or scrolling to another comment. Offline I need to not only ignore a comment/person, but also keep in mind a variety of other factors which don't exist online. Something that will always be lacking offline though is the infinity of possibilities.