Upon a small investigation the issue revealed to be due the comment between enum name and stat of enum code,
enum ia_combat // <this comment>
{
...
}
on game start, the game asks the server to send it a summary of what enums/macros/globalvars/etc. there are in project, and server sends a list of snippets in return. The client then quickly looks through snippets to figure out what are the names to look for in code to determine whether something should be used or not. And, well, for enums I have made the generally valid assumption that with syntax being "enum Name { ... }", the name is what is between "enum" and the following curly bracket, minus spaces. As you can guess from here, the extension was thinking that the enum's name was "ia_combat //Current state of the IA", and thus it wasn't being recognized in "live" code.
Moving the comment to be before the "enum" or after the opening curly bracket fixes the issue; I'll fix this for the next extension update.