Kit

The reasonable middle, which almost everybody accepts:

• Headphones are fine, and nobody objects to them. If the music is for you, this solves it completely. Use one ear in terrain where hearing matters.
• Volume matters more than presence. Something audible at three metres in a busy front-country area is a different thing from a speaker audible across a valley.
• Context matters. A busy popular path near a car park is a different social space from a wilderness area three days from a road, and the expectations really are different.

Where the strong reaction is genuinely earned is a loud speaker in a remote, quiet place. That is a small number of people producing most of the annoyance, which is usually the case with these things.

One thing that changes the arithmetic and is not obvious: outdoor hardware is exposed to weather for decades.

Equippers choose materials and placements with corrosion and rock quality in mind, and in coastal or humid areas that means expensive stainless or titanium hardware. That pushes the per-bolt cost up considerably, which pushes the spacing decision further towards "only where it matters".

It is also why old routes sometimes have spacing that reflects hardware and ethics from another era entirely.

The mechanism is airflow, and once you see it the fix is obvious: the flies are following the smell, and the smell is coming up through the seat into the hut.

The pit produces odour continuously. If the only route for that odour to escape is upward through the toilet opening, then the hut is the odour plume, and the flies are simply flying to the strongest concentration — which is exactly where you are sitting.

The fix is to give the odour a better route out, somewhere else. That is what a vent pipe does. A dark-coloured pipe running from the pit up past the roof heats in the sun, which drives an updraught, and the pit's air is pulled up the pipe instead of through the seat. Put fine mesh over the top so flies cannot use it as a door.

Done properly this transforms the hut. Odour drops enormously and the flies follow the odour to the top of the pipe, where the mesh stops them. It is the standard solution for exactly this problem and it is a one-afternoon job.

One planning note that follows from your reason for asking: the volume question is not only about the confluence.

A crossing gets harder after rain, after snowmelt, and later in the day in glacier-fed catchments — sometimes dramatically. So knowing you are above a confluence is necessary and not sufficient. Time of day and recent weather often matter more than position in the system, and a crossing that is trivial at eight in the morning can be impassable by four in the afternoon.

The practical things that make a day like this go well, none of which require any special preparation:

• Go up gradually within the day if you can. Driving straight to the top and immediately walking uphill is the harshest version.
• Drink more than you think. Dehydration at altitude is easy and its symptoms overlap almost perfectly with mild altitude illness, so people misattribute it constantly.
• Walk slowly. Deliberately slower than your sea-level pace. Most of the misery people report at moderate altitude is from going at their usual speed.
• Avoid alcohol the night before and during.
• Eat, even without appetite.

The rule everyone should know: if symptoms are getting worse rather than better, go down. Descent is the treatment for altitude illness and it works quickly. Nothing about a summit is worth ignoring that.

One detail that surprises people: you probably also have a strong regional effect.

Snake abundance varies enormously by geography, habitat quality and how much the surrounding land has been developed. Two forests that look identical can differ by an order of magnitude, depending on what the surrounding landscape does for their prey and their overwintering sites.

So part of the answer may genuinely be that where you walk supports fewer than you would assume — but the observation bias above is doing most of the work in almost every case I have looked into.