so I'm trying to understand; do experienced dancers and hosts of milongas "cherry-pick" those "rules" (and "etiquette") they believe-in, abide by, or enforce?
As I've said, it all depends where you are and how AT has evolved there. There's also the question:
What's a milonga?
We used to go to a 'tango room' at the local jive meeting. Typically a brief lesson beforehand for jivers run by someone who's well versed in the codigos and AT music. There's a
milonga afterwards. No cortinas. Probably 2 dances in the same vein. Mix of old school, nuevo, alternative - tango, vals, milonga. No particular order. No cabeceo - you go and ask, or are asked. No 'pairs' as such, except maybe if you're known. Dress code - leisurely, some dancers are going on to the WCS later. There are novices there unfamiliar with most concepts of a milonga let alone that there's tango, vals and milonga. Overtake? Block? Explain some move from the lesson? No rules, no enforcement.
There's an organised 'special' milonga with some visiting AT maestros. Tables set out. Lighting. Sound system. Drinks and nibbles. Even somewhere to change. Dress code - smart. Occasional visitor in
Gardel look. Tango outfits and shoes for sale. Wow - you can even see to cabeceo. Music with cortinas arranged in good tanda groups. All very respectful and respectable. People sometimes stand and chat. Any crashes on the floor and everyone involved apologises (well, you do, don't you?). No rules displayed (it's just a useful hall that's been rented). Enforcement - not required. At an almost similar, but more relaxed venue, a
lounge lizard turns up who says he's travelling through. In conversation he starts to mention about picking up women and enjoying holding them. The organiser requests he leave and not return. Another similar milonga and an elderly, but allegedly experienced dancer, criticises one of the followers. He's asked to leave and gets banned for several months.
The tango group monthly milonga. Lights are dimmed so that you can't see people well. There's a few seats around the edge but the room structure requires everyone to be squashed in at one end - about 5 tables deep. Cabeceo? Not to the back of the head! You either ask if you've been sat down talking or resting, or maybe you do cabeceo someone as you walk back to the seating (but it's in a crowd of people leaving and going back to tables). There's the follower on her own because her partner is away on business (or vice-versa). She goes to talk with a couple she knows and gets invited to dance. No idea whether or not that couple she was talking to have danced together yet. Then, of course, there's the couple locked in slow paradas holding up the ronda; or, of course similar but elsewhere, the younger guy racing round the ronda overtaking and undertaking. Rules - well, there's lanes on the ronda and everyone is polite. Enforcement? What?
Rare, public, outside milonga. There's passers-by joining in. There's a couple with a baby strapped on (forgot, that's also happened at the monthly milonga a few months after someone gave birth). There's a couple trying to fathom out the 8CB. Cabeceo - maybe with an experienced dancer, but then there's no cortinas.
Similar setup in another country - Leader gets asked for permission to dance with accompanying follower. Another country - there's a couples section and a solo section of seating. It appears partners in the couples section get asked if they're known. Another country - the (leader) host comes over to talk and invites my wife for a tanda. Sometime later, after other tandas and dances together and with others (cabeceo), his partner (follower) comes over and invites me. Another country - it's a dedicated 'studio' with a floor and bar, but seating is sofas in groups, or armchairs, or some chairs. Cabeceo - how? Music is mainly alternative (OMG, what do you dance to that one?).
Sometimes someone tries to arrange it like they think it used to be back in the
golden age. The expectations are printed on the invite (i.e. cabeceo/mirada - but that's it). If the venue is appropriate, it works; if not, people resort to their own arrangements to get a dance (usually later if frustration at crowding and seating sets in).
The basic
codigo is respect and politeness to everyone. First and last tanda for couples is nice, but it's not universal, or maybe it's just what you arrange yourselves. Or maybe what happens in the
barrio where there's a couples section.
Funny thing about
politeness - my wife couldn't cope with someone from the southern US referring to her continually as
ma'am. But, hey, it's another culture.