Just the opposite! That would be a chat-based game (one of which also was started/discussed here recently- forget the thread, maybe ~1-2 months old?).
There are a couple different approaches, but in theory, it reads like a story. An "In-Character" thread is started by the SG (or one for each sub-story line.) Players post for their character(s), usually a bit longer than a single action, but whatever the situation calls for. After each character has been accounted for (or a reasonable amount of time, depending on the "speed" of the game), the SG posts again, both for NPC's and perhaps also a "summation" of all the action, a sort of synopsis to resestablish a common point in reality and start the cycle again.
Players phrase their posts in terms of "intentions", not assuming too much success nor any responses on the part of other characters. The SG posts actions for NPC's (and any PC's who hadn't posted recently?), and responds with the success/failure/results of any efforts by NPC's, and then the cycle is repeated as the plot/action progresses.
A single post might describe a single action (during combat), or a season or more (during "down time"/study.) It requires a bit of "getting used to" each other, the style/pace of the GM and what they expect, and in general the better the SG describes the situation in advance, the smoother the Players' responses can be.
If desired, all references to dice, math and other game mechanics can be left out or put into "private messages" to the SG, and only IC issues are publicly posted. At its best, it reads like a novel (good or no, depending on the writing), and at the other end of the spectrum more like a transcript of a table-top game, if the players are only posting dry actions (like "I attack the nearest enemy").
The attractions are that if I can only post at midnight GMT, and you at noon, and the SG after 6, we can still proceed at one "post"/day. The disadvantages are that it ~can~ move slowly, but that in part depends on exactly how far in advance players "predict" their characters' possible options/actions in a single post.
Check out some of the games on RPoL for some different examples/approaches:
rpol.net/game.cgi?gi=20278&g ... 1174935508