Coronoro

Simple Plugin which shows whether a registered user has read a Post or not. 
You can also choose to show the number of unread Posts at Forum level. 
This Plugin is an update to the older <a href="https://wordpress.org/plugins/bbpress-unread-posts/" rel="ugc">bbpress-unread-posts</a> Plugin.

bbPress Unread Posts v2

Simple Plugin which shows whether a registered user has read a Post or not.

bandicootmarketing

A ‘New’ label will be prepended to the title of every unread topic and topic that contains unread replies. This makes it a whole lot easier for all keymasters and moderators to identify what’s been happening since last time they check in.

bbPress New Topics

Displays a "new" label on topics that are unread or have unread replies for all keymasters and moderators.

bbPress Unread Posts v2 vs bbPress New Topics