If the setting is not saved the banner would just come back on the next page. But to save the setting at all a cookie needs to be stored. But without consent I shouldn't be storing cookies at all. That's not how other pages handle it, but I believe this is how it should be handled.
Why don't you use Facebook Comments or disqus like everyone else?
I used to use disqus. It had only one advantage: it's not Facebook. But it has quite a big downside: it's slow as molasses. The script is served quite awful: it redirects several times. If I were to autoload it, it would weigh down all Page Speed rankings by at least 20%. There would be some other faster solutions to self host but I want to concentrate on writing the web novel and not waste time spend time setting up some other software and keep the needed servers running. Now I'm using a Netlify construction. Sometimes, technology sucks.
Why do you host on Netlify?
Again, I want to concentrate on writing the novel, not fix stuff myself. Plus, I'm using markdown anyway so any place that handles markdown was just the place to go. I used to use GitHub Pages, but GitHub is missing a lot of features both on the repository side as well as on the hosting side. GitLab happens to be better with the repository side and Netlify happens to be the only place that supports setting custom HTTP headers and proper 30x redirects.