In case you are not using the Beta version of Facebook for Windows Phone (both 8 and 7.5), in order to get access to the latest improvements (and some bugs that come with the Beta package), you might be interested in updating your non-beta/final application. There’s a new version that brings some features to your phone.
You can, with the latest version, batch-upload pictures in messages, you can unfriend someone or unlike something, as well as use the improved inline @tagging capabilities. There are also “navigation improvements, and performance tweaks”, as usual, included in the latest version. Grab it from the source link below or visit the Store app on your Windows Phone for the update.