Not exactly what you describe (much more limited) but a 'best of' for comments nonetheless: https://danluu.com/hn-comments/ https://danluu.com/hn-comments/ I

Not exactly what you describe (much more limited) but a 'best of' for comments nonetheless: https://danluu.com/hn-comments/ https://danluu.com/hn-comments/ I seem to remember another example that was more up to date but can't find it just now (it was also focussed on comments rather than submissions or discussions).