Make sure you change the check on count as above.
When we call postMessage:fromPerson in receiveMessage: we can change our call from:
[self postMessage:[msgComponents objectAtIndex:2]
[self postMessage:[msgComponents [[subArrayWithRange: NSMakeRange(2, [msgComponents length] - 1)] componentsJoinedByString:@":"]] fromPerson:[msgComponents objectAtIndex:1]];
Please double check brackets and that I've constructed that range properly. Granted, this doesn't make for easy reading, but it can be broken up over a couple of lines.