I'm on the fence about this. I've met a lot of decent people, mostly in Warcraft, whose characters have been in pretty much every major Horde or Alliance excursion. They're extremely knowledgeable and usually have veteran, true-Faction characters so I don't have any issue seeing it.
In FFXIV I think using the Primals, because it's almost more of a game mechanic than a real set-in-the-timeline-chain-of-events it becomes a conflict at times if too many people want to claim they're involved in such situations. The major battle(s), however, might not be unlikely at all, though again, I suppose if everyone was there and got time-warped, it might be a little strange.
I don't think it's -quite- an etiquette thing so much as a matter of taste + world-related issue. If SE puts out expansions and patches and those expansions or patches include major events where a large number of people could legitimately be there, I'd find it acceptable to hear a fair number of people claiming to have been involved ICly, so long as it matches their character's goals in the game. I hesitate to throw my lot in just because I've seen such situations abused (Sir, I have a hard time believing that you, personally, overthrew the Lich King with your band of guildies...) because I find when existing people start doing that, new individuals tend to shut down their ideas at 'I'm not ah'posed tah make my characters involved with anything in teh lore' and I don't like to restrict that aspect of roleplay for anyone in any way.
At the same time, some people unintentionally go the opposite route. Again, using WoW as I almost always do as an example, the whole of the issues with Vol'jin and Garrosh and the rebellion were often treated as a series of events that hadn't happened yet while some others were treating it as an on-going thing and others yet believed it was done and over with. It leads to a conflict of interest at times when you have Kor'kron RPers trying to assault Darkspears who're treating the issue like it hasn't even happened.
General acceptance on situations like that alleviate the issue in large-scale communities, but it almost never happens because -that- for some reason is one of those situations where everyone gets hesitant about telling someone what time it is for them. I'm sure in many cases it comes down to OOC communication, and much as I can appreciate the maturity and understanding that that can create, I prefer to keep my OOC communications with another RPer as limited as possible unless it's asking how they want to handle a fight (assuming PVP isn't an option) or apologizing for a really difficult-to-understand typo.
So in short, to review, I think it's a matter of taste and, if done tastefully, contributes plenty to a good RPer's history and I, in no way, would support seeing that appear as an over-arcing, all-inclusive rule that might end with some people who misinterpret or don't give a situation/individual a chance to show their legitimacy being ostracized or corrected needlessly. It's entirely situational, taking in game events or lore events and using them in your character build.
In FFXIV I think using the Primals, because it's almost more of a game mechanic than a real set-in-the-timeline-chain-of-events it becomes a conflict at times if too many people want to claim they're involved in such situations. The major battle(s), however, might not be unlikely at all, though again, I suppose if everyone was there and got time-warped, it might be a little strange.
I don't think it's -quite- an etiquette thing so much as a matter of taste + world-related issue. If SE puts out expansions and patches and those expansions or patches include major events where a large number of people could legitimately be there, I'd find it acceptable to hear a fair number of people claiming to have been involved ICly, so long as it matches their character's goals in the game. I hesitate to throw my lot in just because I've seen such situations abused (Sir, I have a hard time believing that you, personally, overthrew the Lich King with your band of guildies...) because I find when existing people start doing that, new individuals tend to shut down their ideas at 'I'm not ah'posed tah make my characters involved with anything in teh lore' and I don't like to restrict that aspect of roleplay for anyone in any way.
At the same time, some people unintentionally go the opposite route. Again, using WoW as I almost always do as an example, the whole of the issues with Vol'jin and Garrosh and the rebellion were often treated as a series of events that hadn't happened yet while some others were treating it as an on-going thing and others yet believed it was done and over with. It leads to a conflict of interest at times when you have Kor'kron RPers trying to assault Darkspears who're treating the issue like it hasn't even happened.
General acceptance on situations like that alleviate the issue in large-scale communities, but it almost never happens because -that- for some reason is one of those situations where everyone gets hesitant about telling someone what time it is for them. I'm sure in many cases it comes down to OOC communication, and much as I can appreciate the maturity and understanding that that can create, I prefer to keep my OOC communications with another RPer as limited as possible unless it's asking how they want to handle a fight (assuming PVP isn't an option) or apologizing for a really difficult-to-understand typo.
So in short, to review, I think it's a matter of taste and, if done tastefully, contributes plenty to a good RPer's history and I, in no way, would support seeing that appear as an over-arcing, all-inclusive rule that might end with some people who misinterpret or don't give a situation/individual a chance to show their legitimacy being ostracized or corrected needlessly. It's entirely situational, taking in game events or lore events and using them in your character build.