enchantedsleeper
Couldn't that happen even if it was done the other way around, though? If Person A were the one to set up the thread and Person B came to them to give critique, they could still claim entitlement to a percentage of the profit from that.
Well, I think therein lies the difference between feeling out the audience and outright asking for help. If you were to ask someone more boned up on the topic, I'm sure he or she could give you a more in depth analysis, but I'll give my layman's understanding of it.
It's like when a movie is released to certain theaters and the audience is asked to give an opinion on it. I think there was a movie that actually changed its ending based on the overwhelming negative response it received from such a release. In that situation, the people telling the production company that the ending sucked is just them giving an opinion. Yes, it helps guide the overall production of the movie, but their contribution to the film is not the same as re-writing the ending for the company.
Now, in the case of The Death of Robin, DC had already produced two potential endings: ending one, Jason lives; ending two, Jason dies. They let the audience pick from two potential endings that they already written, and the audience contribution of dialing one number or another is minimal.
However, that same company doesn't allow for submissions. I have a feeling that this is partially an issue of liability, but partially an issue of "we don't want to deal with your s**t." In the former, it's possible that a budding artist may have drawn a little ten-page script wherein a fight with Bane leaves Batman with his back broken. Neither the script nor budding artist are accepted, but later down the road, the very same thing happens to Batman. If it were known that submissions were accepted and read, that would leave DC liable for the budding artist to say that the company read his submission and stole the idea. By telling their audience the exact opposite-- that submissions are discarded upon arrival-- it reduces the liability they have, although probably not to a healthy 0%. (At any rate, DC would have the lawyers to back up their position, flood any Johnny Everycomicfan with paperwork, extend the length of the trial, and so on-- so it'd essentially be pointless to try.)
And to get back to the original analogy, if Person A asks for a critique and Person B says the ending sucks, that lets Person A know that the end needs work, but the work would (ideally) be his alone. If Person A asks for a critique and Person B tells him the plot should be changed in specific ways, and then Person A makes the changes of the sort Person B says, I believe he may be somewhat liable for a claim that he owes Person B a percentage, but not entirely because Person B gave Person A more than what he originally asked for. The last possibility is that Person A outright asks for help, Person B offers his opinion on what changes ought to me made, and when Person A makes those changes, Person B can say that those changes were his idea and he's entitled to money from the production.