I don't see anything wrong with that at all ^_^ It's always interesting to see different threads enterchange between themselves.
Although, I would suggest actually posting, not simply making it an OOC comment. If you're looking for someone to post in your thread as a guard, put an ad in the Echoes of the Future board and then you won't have to worry about disturbing another thread to see if someone cares to do a side quest from their current threads.
But if you want to go to another thread looking for someone to join you, do it in post form, not simply in OOC!
I hope that you have lots of fun with your stories!