I don't see that as a problem. If you want to sell a real good domainname you most likely want to mention it in the topictitle, so if it's not in the topictitle you can probably assume it is not a real good domainname.
I would like to propose another rule however, and that is to keep discussions out of sales topics. If you have a problem with a (sales) topic, why not use the
button to report it? Or if you want to discuss it, open a discussion topic.