I have two suggestions to make readability better:
1) include a feature where you can scroll through all the posts / replies from the OP. Similar to the task bar when you do control and F, perhaps. You can do it yourself by using control F, but having a handy little button that scrolls to the next post would make life easier.
2) use quick keys. Lots of websites have them. For example, press l to move to the next reply or k to move back.