Change

[isabell@stardust commento]$ wget https://commento-release.s3.amazonaws.com/commento-linux-amd64-v1.7.0.tar.gz

to

[isabell@stardust commento]$ wget https://dl.commento.io/release/commento-v1.8.0-linux-glibc-amd64.tar.gz

and check if the guide is compatible with 1.8.0