How to be posh AND NOT posh at the same time?

For those not acquainted with the English term "posh", WordNet says it means: "classy: elegant and fashionable", while britishempire.co.uk glossary gives "Posh: Naval This word, meaning 'superior', is said to come from the P. & O. Steam Navigation Company's abbreviation for the phrase 'Port Outward, Starboard Homeward', where the cabins were the cooler in the Red Sea and so the more attractive to passengers.", which seems like a good explanation of the origin of the word. Nowadays, regular people may use it either in a good or bad sense, exactly as you can use fashionable in both senses, something which is liked by many or something stupid which is liked by many.

So, how is it possible that someone/something is both posh and not posh at the same time? Seems like a logical impossibility, unless one does tricks like punning, and pretending the first posh has the good connotation while the second one has bad connotation. But there is another way: one can be very posh about the way they relate to the world and the people they meet (funny this switch from third singular to third plural: I learned last week that it's a way of avoiding the he/she thing when you don't know or don't want to differentiate the sex of who you are talking about - and also learned and learnt, the first one US English - for once they made the sensible choice of removing an irregularity from the language ;) all the better for us poor foreigners) and very NOT posh about the way they behave themselves, either in relation to other people or in simple everyday actions.

One simple example: would you wash your hands after going to the bathroom to take a leak? Given the availability of water, I'd think this is a necessary act, but let us forget for a second about what we would do. The act of NOT washing your hands should be classified as NOT posh in most situations, regardless of whether washing your hands is posh or just hygienically correct. So in order to be posh and not posh, just treat people you meet haughtily (unless they are evidently your peers or superiors) and do not wash your hands when you take a piss...
I.

P.S. If you don't get the meaning of this post, just email me and I'll explain it properly...