Fix bad comment text.

include/status-code/error.hpp

@@ -30,18 +30,18 @@ Distributed under the Boost Software License, Version 1.0.
 
 SYSTEM_ERROR2_NAMESPACE_BEGIN
 
-/*! An errored `system_code` which is always a failure. The closest equivalent to
-`std::error_code`, except it cannot be null and cannot be modified.
+/*! An errored `system_code` which must be a failure upon copy or move or
+non-default construction. The closest equivalent to `std::error_code`, except
+it cannot be modified.
 
 This refines `system_code` into an `error` object meeting the requirements of
 [P0709 Zero-overhead deterministic exceptions](https://wg21.link/P0709).
 
 Differences from `system_code`:
 
-- Always a failure (this is checked at construction, and if not the case,
-the program is terminated as this is a logic error)
-- No default construction.
-- No empty state possible.
+- Almost always a failure (this is checked at copy or move and non-default
+construction, and if not the case, the program is terminated as this is a logic
+error)
 - Is immutable.
 
 As with `system_code`, it remains guaranteed to be two CPU registers in size,