If all you do is have the same person bump the thread with a standard "bump" message, they yes you will be warned, and justifiably so. Try having different people post real messages, like current and upcoming guild activities, fond memories of past activities, etc. With a little thought and good timing, you can keep that thread going current for quite a while with valid content.
Many servers do have lists of guilds in the forums. Individuals from those servers have taken it upon themselves to manage the lists. If your server doesn't have such a list yet, maybe your recruitment officer should start one and incorporate it into your recruitment strategy.