I'm glad [@Odin] posted, as I think his insight is crucial to this discussion.

While I think in principle what [@Inkarnate],[@Lady Amalthea], and [@NuttsnBolts] said is probably applicable to most instances, I think that there are threads where it is far from necessary. I think Odin's example was a good one, and I think further extrapolating from there, roleplays with significant amount of unscripted combat are definitely an 'exception' to the 'rules'. Other categories could include threads that are run partially as games - I would have zero expectation, or requirement, of any of my players to read every other player's capture posts for when they went to hunt wild creatures in my Pokemon-esque RP. Especially true on thread types with expansive player bases where some characters may never interact and we have interactions that are done specifically for singular characters to occupy themselves while they wait for other things to move along elsewhere. The context in which certain posts happens is important.

Definitely probably a more of 'you probably should be reading all the posts on most threads, and most of the posts on all threads' (I'm sort of proud-ish of this line) versus some rigid you must do something in all instances.

Also, definitely not in agreement with telling people to stop roleplaying. Just saying.

EDIT: One more thing, I also think some of the instances where there is something called useful ignorance where true lack of knowledge can create a thoroughly enjoyable, organic (and gluten free), non-contrived interaction. I've had this happen arising from people missing posts where another character was defeated or acquired some powerful artifact (in a game) where it spawned some of the most interesting character conversations I've ever had. 

Yes, there is a line where the ignorance is burdensome, but I've had very few instances where that has been a problem in a thread. That type of ignorance is obvious though because the ones that are in that category are generally apparent at the beginning because they also don't tend to read the introduction...