Could you share the exact requirement? To me, it would be better to create something from scratch rather than extending SCF.
Communities uses HBS (handlebars) template engine OOB which means it uses the framework to initialize, substitute, render, persist etc.
If you plan to use one component of SCF outside the engine, then I'm not sure how would you provide the associated libraries (js/css/global variables etc.) to that component? Even if somehow, you make it work outside communities, then what would be the end-to-end design/data flow of this use case?
Comments are treated as user generated content which would get stored in either TARMK or MongoMK based on the normal AEM site configuration. Hence, how would you plan to sync up these comments across all publish servers in your existing setup and manage replication/cache flush etc?
I assume that you have a solution in-place to these kind of scenarios.
HTH