Hmmmm

Today has been an odd day.  I've been with people I barely know, and with people I dearly love. I was part of a conversation today in which someone inserted a "hmmmm".  You know the kind of 'hmmmmm" I mean.  The kind where you know the person doesn't necessarily agree with what is being said.  Person #1 "Well, that would be exciting!"  Person #2 "That would be, hmmmm."  So I wonder, what does person #2 really mean, what does that "hmmmm" mean?  Why am I bothered by the "hmmmmm"?  Maybe because the "hmmmm" was said by a person I barely know, about a person I dearly love?  Hmmmmmm.