We already have a way to display a post that can be commented (Forum Post with replies.)

We have lists of categories (Forum Topics) since we have lists of pages.

We have lists of pages assigned a given category (Forum Posts in a given Topic.)

Lists can use link meta tags to connect multi-page forum posts into one and the categories all together (link prev, next, up, top, etc.) Therefore this can also be made SEO friendly.

Therefore this feature will be available without further development other than a forum look and feel. The only reason to make use of a plug-in for this feature would be to offer extra CSS and a way to easily setup a forum without knowing all the bells and whistles of Snap!

See: Page feature [core]

See: Categorization feature (tags, hashtags, taxonomy) [core]

See: Comment feature