Re: Etiquette Question
Nobody's going to know what the 'formal method' is, because there isn't one. The site is emphatically hands-off regarding how GMs choose to run their games, so long as those choices don't violate site policies and TOU. So, unless you're running around deliberately throwing players out of your game on a regular basis for no reason whatsoever, you're not going to get in 'hot water' about what your policy is for removing players due to inactivity (and even if you ARE jerking players around and dumping them from your game on personal whim and without any reason, you're still unlikely to get in trouble with the site for that...but you're also likely to start running out of players to join your game in pretty short order...)
The only RPOL policy I can think of that might be applicable is, the GM makes the rules to his/her own game and as long as those rules don't compromise the site (such as ignoring the Adult flag standards and posting restricted content), RPOL isn't going to intercede.
That said, if your standards are too draconian and you dump players too quickly, you'll have a hard time keeping your game populated. The flip side is, if someone's been in your game for a while, and set a pattern for how often they post, and then suddenly stop posting, you've got a pretty good argument for removing them from the game. But how long you wait to do that is completely up to you as the GM. If it's someone that's been in the game for a couple of months, I'd give them less leeway than, say, someone who's been in the game for half a decade (assuming the game has run that long), or if it's a player who has consistently been thoroughly engaged in the game, I'd give a lot more slack that someone who rarely posts more than the barest minimum or generally refuses to interact with the other characters in the game. And, as mentioned, there's also a difference in how to handle someone who has been checking in with the game and just hasn't posted anything versus someone who hasn't even logged in for weeks on end.
If you haven't seen any sign of activity at all after a couple of months, I think you're pretty safe in removing them...if you've PMed and rMailed them in that time frame, you've taken every reasonable step to get their side of the issue and nobody is likely to make much fuss if you remove them from the game at that point. If it's a really rapid-paced game and you haven't seen anything from them in a couple of weeks, you might be able to do it without anyone fussing, but I wouldn't recommend any time frame shorter than three weeks, no matter how hectic the game is, just because RL can, from time to time, throw a pretty hefty wrench in the works for people and your players may not always have the option to get back to a game within a couple of weeks of something catastrophic happening. Some of my fellow players in one game got caught in natural disasters and lost pretty much everything...when you've been totally uprooted because your home was destroyed, checking in with an online game isn't likely to be much of a priority, and they really didn't get much time to post anything about it in advance. So, yeah...I've heard the arguments that there's no reason that someone wouldn't be able to get online within a few days of anything happening, but I've seen it happen. Personally, as a GM? I'll let an idle character sit ignored for months before I even start worrying about whether or not the player's coming back, but I also run a pretty slow game, in terms of posting rates. And I find it easier to leave unused characters as property of the missing player, rather than either deleting the characters or transferring them over to myself to keep them and their information in the game (if someone asks to be dropped from the game, I'll do it and hang onto the character as an NPC, unless it seems dramatically appropriate to kill the character off). It's just that many fewer names I have to scroll through if I'm posting as any of the characters that I HAVE TO RUN to keep the game rolling smoothly.