Correspondent Roberta Brouhard emailed last week that she’d witnessed a 38R-Geary Muni confrontation that arose when a frail elderly man motioned to a woman in her late 30s that she should give him her seat. “Have you ever been seven months pregnant?” she asked him, in what Brouhard described as a stern tone of voice.

A few weeks before, I watched while folks sitting in the decrepit section (I say that kindly, as I am by years qualified) of a bus bound for North Beach had an infirmity versus age stare-down with a man using a cane. And Brouhard described another occasion, when she “watched a young mother with infant in a stroller reluctantly yield her up-front seat to the driver on-boarding an elderly guy in a wheelchair.”

Because signage is not specific enough, the question arises: What’s the pecking order for Muni’s deluxe services, and how does a passenger behave? The following suggestions, in ascending order, are subjective. Feel free to argue, especially if you are reading this on public transit.

•Person with back problem gets no special treatment. As Brouhard says, everyone has a back problem.

•Person with huge backpack (see item directly above) must occupy seat at back of bus, an uncomfortable perch that will force the hiker’s hindquarters to the edge of the seat but prevent other passengers from being smacked. Backpack may not be placed on adjacent seat. That area is reserved for cats being carried to vets for emergency hair ball removal.

•Wet seat rule: Passenger sitting next to seat with puddle on it — possibly water — shall not inform approaching passenger of that hazard. Allow the rest of the crowd the slapstick spectator’s pleasure: anticipating and enjoying the double take when the just-boarded passenger makes a beeline for the seat before discovering the hazard.

•Passengers with no teeth are prohibited from eating burritos on board. If the operator has waived the proscription against carrying food aboard, nearby riders must refrain from stealing even a single french fry.

• The passenger making a sucking sound (prohibited) on a straw (almost prohibited) shall receive the same treatment as the person (above) with a back problem. Only standing passengers are allowed facial expressions, especially the stink-eye.

•Mothers with toddlers and teenage skateboarders reeking of recently legalized substances must share space in the accordion-pleated connector section that joins the two-part bus, thus enabling the latter to serve as role models for the kids, while clearing the aisles near entrances and exits.

•Any pregnant woman gets a seat, but if seats are already filled with Airbnb-ers schlepping roll-on suitcases to the Outer Sunset, the parent-to-be might have to stand. In that case, seated person must offer a lap in which to place the pregnant person’s sack of navel oranges.

•S/he who is strolled is already throned. Person pushing stroller shall be asked upon boarding to provide proof of knowing how it folds. That person shall be regarded kindly, but not so kindly as to lead to expectation of a seat. In a face-off between stroller and grocery cart, stroller wins, but user of cane gets seat before stroller-pusher.

•Person talking to him/herself gets an up-front seat, especially if conversation includes reference to Paul Manafort. On the other hand, person engaging in a non-specific cell phone conversation — “I’m OK.” “It was fine” “I think so” — does not qualify for a special seat, but is left to his/her own device (which may get ripped off, especially if the pattern of the iPhone case is leopard-skin). If speaker is overheard saying “Hi, I’m on the bus,” operator may toss speaker off the bus.

•Person with foot in cast gets a seat or, if all seats are already occupied by persons with reptiles (have seen it) riding on their shoulders, a margin of safety. Person with orthopedic boot qualifies only upon presenting a doctor’s note.

•Wheelchair user pushed by walker-dependent person returning from Costco with a load of paper goods gets A-1 priority, particularly if wheelchair user is holding a leash that’s attached to the collar of a snarling dog.

In that case, passengers less qualified for special assistance should not only give up their seats, but also ... move to the back of the bus, folks. Please move to the back of the bus.

PUBLIC EAVESDROPPING

“When I first moved here, I was able to make a living playing violin on the street. I totally understand why you moved to Pittsburg.”

Woman to woman, overheard on Valencia Street by Ted Weinstein

Leah Garchik is open for business in San Francisco, 415-777-8426. Email: lgarchik@sfchronicle.com Twitter: @leahgarchik