Is there a place on gwern.net for feedback about the website? (I think when set to dark mode, it flickers while scrolling.)
There's a lukeprog-style 'anonymous feedback' link at the bottom of each page. Unfortunately, that's a known bug without a very easy fix (apparently invert filters in CSS, despite sounding easy, are unexpectedly slow, making it easy to display the original white before being inverted to dark, and Said Achmiz hasn't had the spare time/energy to fix it).
The persistency of constant edge-cases and bugs in the dark mode has been frustrating enough I've considered removing it as not worth the hassle; there just appears to often be no way to win, like how you turn dark mode on at all: if you use the recommended CSS approach, then users who forget they enabled dark mode in their OS will complain about the site being in dark mode; if you use special JS theme-switchers to let users opt into it and store their setting in a cookie (our current approach), they will instead complain about the flash of white styling before the site finishes loading!
I'm looking to start a blog for myself. Is it likely I, a fairly strong CS student with no web dev experience, can figure it out in a reasonable amount of time?
How's your Haskell and shell...? No, I wouldn't particularly recommend it as 'my first blog'. It does a lot of complicated things which are overkill in many ways and not implemented in a very user-friendly manner. If you still want to get started, there's a fork from about a year ago which is at least easier to browse/understand: https://github.com/shawwn/wiki
I'd suggest that you consider writing independently of how you (ultimately) choose to publish whatever it is you write.
Without "web dev" experience, any common 'DIY' solution you pick is going to potentially require more than "a reasonable amount of time".
I'd suggest looking at one of the following two alternative avenues:
For [1], you'd just need to figure out the blog software (and maybe, a little, the host's software). You'd otherwise 'get for free', features like an index page, an RSS feed (for people to follow new posts in feed readers), and date-organized 'archives' (e.g. lists of posts). You might need to spend an 'unreasonable' amount of time getting things like comments to 'work' (e.g. NOT be inundated with spam). And changing the blog software would be effectively impossible outside of developing your own extensions (e.g. 'plugins', 'themes').
For [2], you'd just need a public web server. Wherever you're going to school probably already provides you with one. You'd just need to upload your HTML and CSS. You might be able to host server-side code, e.g. PHP, too, but that would depend entirely on what your school supports. Alternatively, you could pay for your own VPS (virtual private server) from one of many different providers, but that may involve an 'unreasonable' amount of time on your part. If you're hosting your own 'hand-coded' HTML+CSS (and/or server-side code) files, you'll have to implement things like an index or comments (or an RSS feed) yourself. But an index could just be a single static page to which you add a link when you publish a new blog post (which is also just a static file).
There is (of course!) many 'intermediary' solutions available too – but, even for professional web-dev people, just sorting thru them can take an 'unreasonable' amount of time.
One 'genre' you might want to look into are what are called 'static site generators', i.e. code that generates a (mostly) static site, e.g. HTML/CSS/JS files, from some more abstract 'source'. A lot of them allow/require you to write things like posts as Markdown files. Some of them can work with GitHub/GitLab/etc. 'pages' for publishing to the Internet. (You could even use GitHub for comments. One interesting idea I saw floated was to require commenters to create a GitHub pull request to modify a post and add a comment.)
And somewhat outside all of the above possibilities, you could just post whatever you write on this site (which supports 'personal' posts) or Reddit, a suitable forum, or in publicly accessible Google Docs docs – there are a lot of possibilities like this and this might be the overall most sensible solution (if you definitely don't want to necessarily spend an unreasonable amount of time learning the tools that make up other more prototypical 'blogging' solutions).