Great question! No, I haven't. I lowkey forgot I had cohost userscripts, and I assume you're talking about my contributions to @mintexists's Markdown Plus userscript since my other one is dead.
The IDs are just big random numbers basically, they should just not collide with any cohost chunk or other userscript chunk. The injection isn't super loadable-components specific, it's mostly just webpack stuff.
I don't think any userscript I've written has touched SSRed components? but yeah hydration is a fuck, my advice is probably to just... wait for react to hydrate before you run your stuff? maybe check by doing something like Object.keys(document.getElementById("app")).find(k => k.startsWith("__react"))
