I've been using Hugo for the past 3 years. Biggest lesson I learned is to just fork the theme you're using and don't use submodules. There's no rush in keeping your theme up to date. Also you have complete control over the theme when its forked. I've only had stuff break on occasion when updating to a newer version of Hugo, had to change a couple things with the theme which did not take too long to fix. Curious to see how comments will be implemented though. Does not sound straightforward to add to a SSG.