Earlier quoted context omitted.
If recover is used in a file you never read, is its complexity relevant?
I think what's happening here is pcwalton is a language implementer, so when you talk about 'conceptual complexity' he thinks about how the feature is specified, whereas you or I think about how the users of the feature think about and use it. We're all talking past each other a bit, I think.
The whole reasoning behind not supporting a ton of features in Go is that excuses like "don't need it? Don't use it!" are invalid when it comes to programming language features. And nowhere is this more relevant than for a feature that can unwind the stack without warning.