The mods being distributed as manual diff application instructions and then auto mod installers became a thing. Also called all caps MODs to distinguish them from forum moderators.
This is the hardest nostalgia. I'd forgotten about the manual diff! I was doing this at 13 and was basically what got me started in PHP development in general.
And doing the equivalent of partial compilation by just dragging and dropping your php install over FTP and telling it to ignore the unchanged files. Then writing .htaccess files everywhere to tell Apache what to do if you had a 'front controller' pattern.
20 years later and people are doing CGI through WASM or lambda so they can use their language of choice. Full circle as always.