I will be glad to answer this. The two most popular boards on the site are Mtf Talk and Ftm Talk. You need only look at the number of pages found on these forum. Or the number of new posts made to these boards in a week.
Part of the way the site is set up is so that topics can be easily located and researched. Suppose I was new to the site and I wanted to research "testosterone pellet implants." Where might I look?
I suppose I could look through over 400 pages of posts on the FtM Talk forum. Or I could look in the forum dedicated to HRT: "If you are interested in information about HRT or are currently on HRT and wish to discuss the issues we face, this forum is for you." Not "boy territory," not "girl territory" - transgender territory.
I understand that the original poster wants to get as wide an audience for their topic as possible. Typically, I don't move posts off of the MtF or FtM talk boards until they have rolled of the front page, and then for archival purposes. When topics do roll of the front page or two in the FtM or Mtf Talk forums, they are usually dead and lost forever.
It sometimes happen too, that a post is made on one board that has implications for all of our members, such as what is needed to a name change or gender marker change. Hence, moving over to Legal Matters: "To discuss the legal side of transition, including changing name and gender markers on legal documents."
The other forums exist for a reason. It is to improve the utility of the site. So in managing the "usability" of the site, I try to take into account the needs of the original poster with the needs of future members or visitors here.
I usually leave a notice of the locations change (called a "redirect") up for a few days, until I see the OP has posted again in the topic. Furthermore, you can always find a moved post of yours by checking your post listing in your forum profile. If a topic gets deleted, as sometimes happens, then you might not get a notice.
I hope this helps.
I am open to suggestions on ways to improve the management of the site. And keep in mind, we have staff openings for anyone who wishes to tackle these logistical challenges.