first of all, a big thank for this innovative forum with using of last technologies like responsive design thanks to HTML5 and CSS3.
I would suggest to add a new setting beside "Hide topic messages" and "Enable infinite scrolling" : the possibility to display directly in full rendering aspect the forum instead to click to "read more" link. This option very usefull for small forum allow a logical display with the right formating choosen by the writers. By example, it is indeed curious to see the quotes text part mixing with the answer.
If you don't want to have a too big user settings part in the frontend, this choice can be put else in the backend part.