> If there are many client programs sending SQL to the same database over a network, then use a client/server database engine instead of SQLite.

https://sqlite.org/whentouse.html

Judging from a quick glance, this particular library (Isso) does not seem to be the case of "many client programs sending SQL to the same database over a network". There is only one server as a "client" program, sending SQL directly to the database, not over a network. If so, I'd tend to agree that SQLite is suitable for its purpose.

I've hit r/w concurrency limits on relatively light usage; WAL mode solves it very handily (stops reads and writes from competing, makes only writes compete), but it also means that backup becomes just a little less trivial.

I feel quite the opposite.

I can host a small website for free in places like Heroku. I can use Disqus on S3/Cloudfront, and similar alternatives.

There's a bunch of ways now to easily run a site in a docker container somewhere and connect to a managed DB.

sqlite? That requires me to manage a whole VPS just so I have disk access to it. For my personal site, that's more than I'm willing to get into (also note: managing servers is part of my job description).