If you want to enable or disable some of the basic features of your board, this is the place to go. Here you can allow and disallow for example username changes (Allow Username changes) or the creation of attachments (Allow Attachments). You can even disable BBCode altogether (Allow BBCode).
Figure 1.4. Board Features
If disabling BBCode completely is a bit too harsh for your taste, but you don't want your users to abuse the signature field for tons of images? Simply set Allow use of IMG BBCode Tag in user signatures to "No". If you want to be a little bit more specific on what you want to allow and disallow in users' signatures, have a look at the "Signature Settings" form.
The "Board Features" form offers you a great way to control the features in an all-or-nothing way. If you want to get into the details on each feature, there is for everything also a separated form which let's you specify everything from the maximum number of characters allowed in a post (Max characters per post in "Post Settings") to how large a user's avatar can be (Maximum Avatar Dimensions in "Avatar Settings").
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