Doesn't apply to most other stack exchange websites

Excellent.

Works well with https://addons.mozilla.org/en-CA/firefox/addon/widestackoverflow, too.

Exactly what I needed, thank you. Better than the other addon that just blocks HNQ

Does exactly what is says (removes right sidebar of stackoverflow) and one reason I like it much better than using Stylus is that it only needs permissions for stackoverflow.com