Hello
I don't remember which specific threads were rejected, but if they were rejected it's because some user reported an abuse and I agreed with that.
Most of the questions that are opened daily in this space were already asked and answered before. If a question is asked and answered dozens of times, it is not necessary to have any new thread with this question, so it will be rejected, as it will not add any value to the space.
It is not the moderator task to search and provide links to these threads. Therefore, if your thread was rejected, it's because it has already been seen on the space and I suggest you to research again on the same topic.
At last, I suggest you to read the excellent blog Asking Good Questions in the SCN Discussion Spaces will help you get Good Answers before opening a new thread.
BR
Caetano