This is a very interesting topic. Una, first off, I want to emphasize that your dad was a bozo in saying that! I am always struggling, when I look at your WIW pics, to see *any* of the negative features about your bod that you mention :). Seriously, you look so fit, long-limbed, and athletic to me--like what I imagine a rock climber would look like!--I truly don't see any unusually big shoulders, large bosom, lack of waist, etc. etc. It's actually hard for me to imagine you any smaller than you are. Okay, just had to say that...
Re. your point about honest feedback. I think it's tricky. We all have different taste, which of course is completely subjective. And we all have different levels of comfort regarding just how much honesty we want to hear! I always seek absolute frankness whenever I post ("Frank feedback always welcome") and I expect to get some negative or at least lukewarm responses. But I sometimes I don't, which makes me think that people who feel less-than-positive just don't post a reply.
I think sometimes people don't want absolutely frank feedback. It can feel too vulnerable to open yourself up to that, or too hurtful if someone says something harsh. When someone does want frank talk, and I'm not too enthusiastic about the outfit or whatever, then I will offer it in an honest but polite way. Otherwise I focus on aspects that I do like, or I just don't post a reply. It's tricky, because I realize what I like, purely based on my own ideas, may not be congruent with the person's style or taste, etc. Ditto the reverse...And I'm also a person who values trendy things that are bold and risky somewhat more than the whole "flattering" thing, which to me usually seems to mean "does it make you look smaller/thinner/show off your body?" if you get right down to it. I don't always want to necessarily "show off my figure" or whatever (I might value something different with that look, e.g., a trendy loose-fitting silhouette), so someone might think that my outfit is "unflattering." So there are different criteria, really, for every person, so sometimes we aren't even speaking the same language.
Enough rambling :).