There are a lot of great thoughts here that make me re-think the term high functioning alcoholic. I would have considered myself a high functioning alcoholic but wore it more as a mark of hypocrisy and shame rather than pride.
What it meant for me is that as my alcoholism progressed, many aspects of my life also progressed in a positive direction. Home life was stable and the marriage relationship strengthened and deepened over time, we made the move from renting to owning our own place, career progressed with promotions and salary increases, there were awards for outstanding work place performance, a mountain of past debt was cleared, etc. Externally I had a dream life, but no one knew that so many days on the way home from work I'd buy a bottle of vodka, go into the first alley I could find without too many people to pop the lid and get a head start before I got home and kept on with a typical night ending with me at my home office computer watching sappy YouTube videos and being all weepy and deluding myself into thinking that all the emotion was actually a gift to be able to feel.