What does it mean to say "yes"?

I went to Ropecon with Ville Halonen last weekend and got to play in Steve Segedy's and Jason Morningstar's games. Ville raised an interesting point at our blog and opened the discussion about "what does it mean to say yes"?

http://blog.guildredemund.net/2015/05/18/what-does-it-mean-to-say-yes/

This reminds me of a play session of Pathfinder.

During a particularly annoying encounter, a rat-snake-thing kept going beneath the floorboards to avoid damage. This resulted in about 20 minutes of our characters standing around, unable to strike the thing, waiting to get bit.

Eventually I said, 'okay, I'm a paladin, I'm going to dump tons of water into the hole until the thing is forced out.'

Saying no (our DM's response): "No that's stupid"
Saying yes the wrong way: "Sure, even though I think that's stupid"
Saying yes the right way: "Sure, but now the ground is really slick and if anyone moves they have to make a roll not to slip"
Saying yes the Lumpley way on a 7-9 roll: "Sure, but now the ground is wet and slippery, and ten giant rats that had been sleeping beneath the floorboards pour into the room, diseased and pissed"

The whole DitV quote/rule is "Say Yes or roll dice." The direct implication is that you can't--as GM--just block a player's assertion or attempted action. It also covers the implication that, if you as GM don't have an active reason to prevent the player's assertion, just go ahead and default to saying yes (a tradition emerged in some RPGs of "if it's not in the rules, it can't be done" and I think Vincent was pushing against that 'lame' and passive approach).

I have also heard of the improv 'rule' called "Yes And" which is a shorthand for the general improv etiquette that you don't contradict, block, or ignore another participant's contributions.

It seems from that blog post that you've adopted the more-expansive interpretation from improv over the rather-specific policy in DitV that is a guide for being a proper GM for the game.

But I could be totally mis-recalling or mis-interpreting intentions (of you and/or VB). :}