I am using Shiny to create interactive graphs on a website, but it doesn't seem to have support for things like comment threads, or database storage. Are you supposed to somehow use Shiny within another language?
This question was downvoted, and I hope I won't lose scarce rep points by answering it. I can't speak for the Shiny development team, and I'm only a novice Shinyapps developer, but ...
It seems to me that Shiny aims to make it easy for for R programmers to build small to medium-sized, self-contained, web-based graphic-centric interactive data-analysis displays, without adding an unreasonable amount of code to what they wrote to do their actual work, i.e. the analysis. This is a fairly common requirement for researchers and practitioners (as opposed to full-time professional developers) coming from the R heritage and culture (stats and data science). Shiny achieves this aim pretty well!
You can find out more about the kinds of problems that Shiny aims to solve by going to the source. Note that it says Turn your analyses into interactive web applications, not Build a full-service website with interactive chat and a backing store. It sounds as if you want something different in scale and kind, and you may be wasting time by trying to shoehorn your requirement into the Shiny problem/solution space. I've occasionally hammered nails into wood using a pair of pliers because my toolbox was at the bottom of the ladder, but that didn't make it the right thing to do!