append links with unique number string

you should probably create a CPT with hierarchical structure like pages and support for categories and tags if needed. Once you have it each story can be a “main” page and each update its child. You might need to decide how to generate RSS and email updates for it if it is required.

Another alternative is to base what you do on the P2 theme. What it does is in a way exactly what you want. I think that the main problem there is sharing the update on social networks and you might need to learn how to share html fragments. Main drawback that I can see right now is how do you handle “real” comments, and again RSS and email udates.