Cedric Plante writes in:

How apt. This question strikes at the heart of gaming. 

Gaming is about communication. Dice, stats, rules, all fall to the wayside in tabletop role playing games behind the essence of "What do you do?" [Tweet this!]

I was browsing G+ and saw someone reference a Reintsian dungeon crawl. It wasn't D&D or B/X - it was Jeff. [1] (You can search G+ for the term here!) When talking about D&D, it is not the way combat or skills are handled that differentiates the game, but the communication style in playing it. There is no question that communication is part of gameplay.

I am a proponent of Old School play. [2] In old school play, the player is the person tasked with making choices. The idea is that the player puts themselves in the role of explorer, not that of an actor playing a part.

I ended a game in media res last week. This week different players showed up. The old characters were gone and the new players and their characters were there.

From Drawing & Dragons for LoFP

My priority is not creating a naturalistic environment that reeks of verisimilitude. My priority is playing a fun game with my friends.

Players always communicate as players and rarely as their characters, even when interacting with NPC's. Players discuss options as a group. As a general rule, anything they are saying both takes time within the game and can be heard by people standing nearby. These are for the game purposes of encouraging focused play as a measure of player skill (planning quickly to avoid random or wandering monsters) and keeping play focused on adventure and not inter-party squabbles and rivalry (No discussing killing players or hirelings or other NPC's without consequences).

When players take action, that action occurs. Occasionally when players have engaged in 'take-back' behavior, I will nominate a rotating party leader and will enforce that until players begin to take responsibility for what they say. Other games (run by a certain notorious narcissistic blogger who does not deserve a link) allow no table talk, assuming that everything said is always said and done.

The communication structure in gaming is based around IIEE. (Intention (announcing the action), Initiation (starting the action), Execution (completing the action) and Effect (consequences of the action).) In my games Intention and Initiation are conflated. Many players will attempt to state Intention to bait the Dungeon Master for Execution.

This next part is so important.

I bypass the Intention/execution end around by using player agency. "You have options A, B, and C. Here are the consequences of each. Choose."

E.g. "You may remain where you are, or you may step out into the hallway, but you feel fairly certain that doing so will place you in view of whatever fired that arrow, or you may attempt to move back, either fleeing or hiding behind party member B for cover."

Players are responsible for acquiring information about the situation themselves. There are two ways this happens.

1. They ask. I tell them.
2. They ask. I tell them the cost to find out.

Consequences

Yes.

This is a fairly standard group dynamic. Peer culture has a huge influence on behavior. It can be situationally addressed by (politely) telling everyone to shut up and asking the player what his action is without interference from the rest of the party. In general, however, this should be considered a positive thing. You do have the power to say "Discussion is over" and then ask for actions, free of input clockwise. Or look at other game resolution options and systems that allow choices to be made without input from all the players.

"Sometime it also feel like that in-game communication limitations could lead to interesting in-game situations. Like removing "on the spot" decisions."

When you design a dungeon or adventure, that is literally a truth of what you are doing. You are designing it. There is a standard mode of play, but certain situations can create an 'on the spot' decision. The key is it should be a consequence for player action. Make sure that whatever is causing the timed situation is clear (a stopwatch, a count, etc.) and driven by player choice. Then they are on the spot. Again, it should be an intended design, and not simply something done to frustrate your players. 

[1] Note that I'm not saying that system doesn't matter. Clearly communication in Bridge is part of play, as it is in Burning Wheel.  But we are talking about D&D which is it's own broad spectrum thing. You can design an RPG about communication as a game-play element, that makes it its own game. When speaking about D&D or the base role playing experience, it is much like talking about poker. Even through the hundreds of variations, the structure of poker and the necessary elements of communication (tells, bluffing) remain the same, even if minimized to the point of irrelevance.

[2] I've played new games, from Vampire to 4e to Dogs in the Vineyard to Microscope and more. My preference for old school play is no statement on the validity of those other play-styles. It was fun to play those other games! I imagine my assertiveness of the virtues of old school play have caused people to assume that I'm saying something negative about those other games. When in truth, when played as designed they can be fun! (Though I will admit, I want to add about 1000 caveats to that statement.)