Usually there's an informal posting-order that may or may not have much slack allowing tiny 1x1 convoes to occur.
-Lack of this result in 'rabbit-posting' because it looks like the posts are mating like rabbits.

There's also players that are not directly interacting with your character, but when they come into contact, are going to need to bring you up to speed/brought to speed on what either respective sub-group was doing.
-This may even abuse 'fluid time' since posts can take-place in flashbacks and time-skips independent of other groups, so getting things to mesh again can be tricky. For extremely-divergent sub-groups it may be necessary to create separate threads within the same continuity.

And lastly, it is possible to go AFK, and hand the controls for a character to the group in 'auto-follow' where the character is present, but just not doing anything outwardly worth mentioning (alternately, are directly controlled by someone else as an NPC).