Almost all our code is realized in plugins, pages, modules, layers and an advanced theme according to Q2A specs. Just le last feature, setting rep gained in meta go zero, required a change in the core code. I did not find another way to realise that because the count engine is not accessible from outside and does not care about categories. I have left all my programming principles, but have marked these positions (there will be more to realise all requirements) using a mark that is searchable by a developer.