One issue that has come up many times in roleplay, with many players, is that of "invisible poses" in multi-PC sessions. Namely, it goes like this: "Joe swings his sword at the red monster. Carl notices a blue monster standing right behind Joe, and thinks that Joe is in trouble."
Most likely, the GM has whispered or paged to Carl some information, advising him that, from his perspective, he sees a blue monster that Joe cannot. The purpose of this is simply that the GM's job is to report to the players what they see, hear, or otherwise sense, which is not immediately conveyed in dialogue and poses with other PCs. Carl could well choose to shout, "Hey, Joe! Look behind you!" Joe would then have an IC reason to change his course of action, and benefit from this observation. Or, Carl could choose to deal with the blue monster himself. Or, of course, Carl could simply stand there.
If Carl's player simply types something like "Carl notices a blue monster," this really does nothing for anyone else. How does Carl look when he "notices" something? There is no reason for this to affect how Joe deals with the red monster. The GM could have just as easily spoofed, "A blue monster sneaks up behind Joe ... though he doesn't notice it," and accomplished much the same thing. It could be significant, in the grand scheme of things, that Carl notices something and chooses not to say a word ... but this presents certain difficulties to multi-player roleplay.
In a solo log, with just one PC, the GM controls all the NPCs anyway, and routinely has NPCs not acting upon facts that they, IC, should not be privvy to.
For a multi-PC log, however, Joe's player now knows that Joe is in trouble ... and, IC, he has no good reason to do a thing about it. Joe's player could be tempted to come up with a good excuse for his character to choose to spin around just in time to see the blue monster ... but is that really good roleplaying? Is he acting upon information his PC has, or what he, as a player, has?
To further complicate this, Joe might well have good reason to look behind him ... but Joe's player may be concerned about being made out to be a bad roleplayer. To some extent, roleplay depends upon the problem-solving and guessing skills of the player, not just the PC. Having been given, OOC, information the PC is not privvy to, Joe's player no longer has the opportunity to try to guess whether he might have another opponent sneaking up on him. It's no longer a "lucky guess".
Now, it could be that Carl's way of "noticing" this blue monster is to stare intently, in wide-eyed horror, at a space just behind Joe's head. It could be that Joe has due cause to notice that Carl is noticing something. If a player wishes to acknowledge that his PC "notices" something, it would be best to state the pose in terms of what can be observed. After all, the GM usually only spoofs information that all present PCs have access to -- with certain exceptions, for the sake of convenience.
Another side of this issue is the matter of making other "observations" that don't directly pertain to what actions PCs might take if they had access to this information ... but which other PCs might still react to. For example: "Joe strikes a heroic pose, having managed to defeat both the red and blue monsters, with nary a severe wound. Carl thinks that Joe is a pompous fool."
If Carl had stated his thought aloud, Joe just might have something to say in response. He might laugh it off, he might make a retort, or he might try to bash Carl's head in, among other things. Carl might have good cause to keep his mouth shut. However, in a log shared by multiple PCs, it really isn't terribly fair to be throwing in insults and jabs that other PCs can't respond to. It doesn't even have to be a direct insult. It could simply be, "Carl observes that it is highly illogical for Joe to be proud about fighting the red monster, when it is plain to see that things will only get worse."
For all the pose says, one might assume that Carl is keeping a complete poker face, or even a facetious smile all the while he's thinking this.
Some GMs dislike this kind of non-interaction in their role-play. If your PC is just going to stand there and think, making "peanut gallery" comments that nobody else can respond to, then you might as well just sit in the FST3K room and throw popcorn at the screen. If it's your idea of making commentary on how the GM is running things, then you're better off telling the GM plainly, if you want anything to actually change. If it's a matter of you not liking how other players are handling their PCs, there are far more straight-forward ways to deal with such issues.
In a solo log, you can fill the lines with as many thought balloons as you like. In a log that stars only your PC, it's all the more worthwhile for the "audience" to know just what's on the PC's mind ... especially if you don't actually do much of anything. However, be forewarned -- some NPCs might be especially perceptive. Some GMs don't assume that every sneaky PC is born with a perfect poker face. If you play a "cheerful and happy" PC, according to your write-up, but all you do is sit around and think grumbly, critical thoughts, the GM is going to develop a mental image of your PC being a ne'er-do-well grumpy-gus who goes around with a cloud hanging over his head. There comes a certain point where some of that cynicism in your PC's head just has to leak out somewhere.