I've seen some great discussion on this meme, on relatively small prompts, where many suggestions and scenarios have been added to complement it beautifully.
For example, the Grant/Strange uniform kink prompt (page 18) started as something relatively small and expanded wonderfully in the replies. It's actually a brilliant example prompt to use for three reasons: 1. the OP was fully involved in the discussion, 2. while many thoughts and ideas were added, they were all on-topic to the prompt itself, and 3. it got a fill that was based upon the discussion rather than the prompt (something the filler mentioned) but as the discussion was so to the point of the initial prompt it still worked and the OP was happy.
Hijacking this prompt would have been something like: "I really can't see this happening. It would be better if it was actually Strange wearing Grant's uniform because Strange sees Grant in his uniform all the time and would be immune to its charms - somebody should write this instead!" That's completely changing the prompt and also criticizing it - the whole frowned-upon shebang! That sort of thing should go in a new separate prompt.
It's tricky to pin down exactly (although I've very rarely seen hijacking on this meme and don't think anyone should worry too much) and I'm sure the mods will do a better job explaining it than I have here, but as long as your ideas and suggestions fit the prompt and are respectful to the OP, they will hopefully be appreciated by them.
Re: Recent issues with prompt-hijacking, criticism, and spamming
For example, the Grant/Strange uniform kink prompt (page 18) started as something relatively small and expanded wonderfully in the replies. It's actually a brilliant example prompt to use for three reasons:
1. the OP was fully involved in the discussion,
2. while many thoughts and ideas were added, they were all on-topic to the prompt itself, and
3. it got a fill that was based upon the discussion rather than the prompt (something the filler mentioned) but as the discussion was so to the point of the initial prompt it still worked and the OP was happy.
Hijacking this prompt would have been something like: "I really can't see this happening. It would be better if it was actually Strange wearing Grant's uniform because Strange sees Grant in his uniform all the time and would be immune to its charms - somebody should write this instead!" That's completely changing the prompt and also criticizing it - the whole frowned-upon shebang! That sort of thing should go in a new separate prompt.
It's tricky to pin down exactly (although I've very rarely seen hijacking on this meme and don't think anyone should worry too much) and I'm sure the mods will do a better job explaining it than I have here, but as long as your ideas and suggestions fit the prompt and are respectful to the OP, they will hopefully be appreciated by them.