Support. But sometimes people don't realize that another thread has been made. 1 Thread with 100 comments is going to get more attention than 10 threads with 10 comments.
Its not a big deal though? You can obviously just give a link to a moderator or something and show them the date you have uploaded the thread and prove that you posted the idea first and that you should be given credit. And the moderator can simply just lock and archive the thread (like what @Flazer has mentioned) and finishio!! Its pretty simple to get rid of a thread that has your ideas on it. Soo ill stick with a neutral on this one.
But then thread makers would need to research on what threads have been posted and by who and when. If it's not spam it should be fine. In my opinion.