Another important thing about Combat Climber is it does not prevent you from still allowing the PC to try it with a (suitably challenging) roll. Combat Climber allows it without a cost, so why would ruling it can be attempted with a cost be prohibited? That makes no sense.
Yeah, if you wanted to do some sort of ruling where someone could hold onto a sword while climbing, you could just put on a harsh modifier (+2/+5, maybe dependent on the size of the weapon). Hell, if you wanted to you could have someone swing a two-handed weapon and make a crazy Balance check to keep their feet in place if they so desire. Failure would be, to put it lightly,
bad, but you can totally make that sort of ruling. I probably wouldn't (or I'd be pretty clear that this is not a good thing to attempt), but there's no rules preventing it.
Same with the Dandy feat: what it does is lock in a way for the player to do something, rather than the GM making something up. If you want to change a rumor and don't have the Dandy archetype, you just have to wheel and deal with the GM in a way that the Dandy simply does not. That's the benefit of the feat: it's not that it necessarily prevents other players from using those sorts of actions, but rather it
guarantees that player from being able to do it.
Another good example of this is
A Home in Every Port. You can find free lodging if you spend 8 hours in a town or village. There's nothing that says you can't do that with other players as a matter of course; you spent 8 hours as a cost and now you get free lodging for a night. But they never get that guarantee, while someone with that feat
does.
Hilariously, the pebble issue did come up at my table. In 3.5 there was an elementist wizard who could detect the presence of rocks and wanted to know how many auras were in the cavern. Haha.
The old guys in my group often tell about the one time in a wargame that someone had a gun pulled on them (it ended with no one hurt and that guy obviously hasn't gamed with them in 30+ years since he had real problems), and it's always been a topic of discussion as to what would be the thing that causes you to draw on a guy.
I wouldn't do it for that, but it'd be
close. And I would make that fact known to my player if they wanted to do that again.