I play all my pen and paper games on IRC these days. It's a sad development that is a result of being separated by time and distance from all of my players, but it's enabled me to play with people I would otherwise have never met. I prefer playing in-person: more can be said, faster, and the game moves along at a rapid clip when everyone's around the table. I have a stable of voices I like to trot out for in-person games that are never used on IRC. For me, it's a suboptimal playing choice.
But I've been there for a long time now, going on three years. Before that I played on AIM because all the people I played with had gone to school (so had I) and that was the only way we could keep playing. I've discovered that there's a cult of players and GMs on IRC that disdain the use of dice in the game channel because it clutters up play. This seems to me to be an extension of the issue that people have in-person around the table: too much OOC chatter.
But, is it? Is too much OOC chatter even a problem? Let's look at it from an outside perspective without any bias. Talking out of character has, in my experience, been an issue mostly for the reason that it eats up valuable game time (after all, we don't have all day to play!) and thus detracts from the game by giving us literally less game to play. This is a problem; yet, players and GMs alike love to chat, particularly if they don't see each other all the time. Out of character chatting occurs outside of the game because the people playing the game are friends. This is a side-effect of something good that in itself is not necessarily evil, but must be moderated.
Now, the second issue at hand is rolling dice in the same IRC channel in which the actual gameplay is taking place. OOC talk is likewise relegated to a separate channel, one in which dice are probably also rolled. The first and most important issue that this addresses is immersion. How do I know this? I've been told by the people that do it. I imagine that the secondary concern is leaving clean transcripts for later viewing. But what exactly does rolling dice have to do with immersion in the game?
There is a school of thought that insists that the action of the game is sacrosanct and that the curtain should never be pulled back on the mechanics that are running it. This attitude, to me, is mystifying. I don't see how the presence of dice interrupts the illusion of inhabiting another person; they simply allow one to see into the workings of the world.
This is just an observation; I'm far from certain what it is that causes this, nor what it means. It's just another one of those strange things that go on in the roleplaying world.