I want to install new shock absorbers for my skoda octavia I 1.9 TDI 2002 model. My mechanic told me to install bilstein comfort shocks with stock springs. Will this make the ride harsh when compare to stock absorbers? My stock dampers weakened a bit. Please recommend.

It shouldn't make the ride harsh. It will feel more taut than you're used to, but unless you installed lower rate dampers than new standard units you'd get that regardless of where you sourced the replacement dampers from, simply because the ones you've got are worn.