Regarding being just another taint, canim, symbiant, etc... Kunren pretty much has the gist of it. Those were just the easiest examples to use.
Nothings really changing in how we approach these types of major character-changing events. We always give people an out. It's not like one day you'll just wake up and BOOM, your entire world is flipped upside down. Well continue handling that kinda stuff the same way we always do.
To give some past experiences as example... You may find yourself knocked out during an infested invasion, waking up some minutes later in another location. The next day, you may start to hear voices in your head. These voices might urge you to certain actions or reactions to others. You might sense a feeling of paranoia, you may hear ,'Don't trust her, she lies!' when talking with one of your close friends...
It's up to you how to act. You could resist the voices and urges. Confess to your friend something isn't right. They may have you try out some random home remedies, maybe take you to an "expert" who has you drink a strange tincture, whatever, and then everything's back to normal.
Or you could subtlety start to act towards your urges. You listen to the voices and seclude yourself from others. You might be drawn to some random nest area. Eventually you form a relationship with the presence in your mind, and over time you come to realize you're a symbiant.
Or (and I think this is what happened in this specific example), you could completely ignore every single message we send you, not reacting one way or another, and we sigh to ourselves, grumble a little bit, and move on to our next thing since you're clearly not interested.
This was a real scenario that was offered to a player before. This is how we normally handle stuff like this, and the event flag isn't really changing that. It's always going to be a forked road and there will always be an out. It's not like just because you have the flag set we are going to start making the decisions for you. It's more like, we're not likely to invest the time setting up something like that if you don't have the flag set.
Lastly, I know I don't really run many events myself personally, but I think most of the team here knows that I am ADAMANTLY against OOC coordination between players and GMs about future events. Just saying "Hey, somethings going down, you might want to get online" is one thing, but I believe it a major taboo to actually have a two-way discussion with a player planning an event around them. You're free to give us your story and your oppinions and ideas, and we'll listen to them and take them into consideration, but we as GMs should not be giving a back and forth planning and sharing all the details of an event.
Sorry for any weird typos/auto correct failures, this was typed on my cell phone.
[GMCHAT Uyoku]: Octum is when the octumbunny comes around and lays pumpkins everywhere right?
[GMCHAT Rias]: Dimmes says "oh hai :) u need healz? ill get u dont worry thaum lasers pew pew pew lol"
[CHAT - GameMaster Rias would totally nuke Rooks]: Here's how elemancy works: The freeblegreeble and the zippoflasm have to be combined with the correct ration of himbleplimp, then you add the gargenheimer and adjust the froopulon for the pattern you want, apply some tarratarrtarr, yibble the wantaban, and let 'er rip!