The not being able to create an account yourself, is traveling traffic away. Now I'm pretty sure why this is so, but here is a suggestion that could help:
Allow people to make accounts, but, make it so that account has to be verified by the admin. This way, you can stop spambots and whatnot. You can also add a spambot resistant thingy to the registration. Writing the numbers down from the images (or letters), or you can ask it to spell something very specific like "doDAY i GOT home to WoRk." it works 2:
Allow people to edit their posts. Its a bit of a mess otherwise...3:
Spoiler tag! Its great! It can make posts, especially Conlang threads, incredibly neat and organized. You can disable it through signatures as well.4:
center coding and more BBcodes! It will help! :3And 5!
If 1 isn't liked or if you don't want to do it, you could do this:
Make a better announcement about contacting the admin for an account. For example, you could recite this message when someone presses the "REGISTER" button, or make it a forum announcement above the forum.