u3: cleanup comments about snapshot system limitations
//! ### limitations
//!
//! - loom page size is fixed (16 KB), and must be a multiple of the
-//! system page size. (can the size vary at runtime give south.bin's
-//! reversed order? alternately, if system page size > ours, the fault
-//! handler could dirty N pages at a time.)
-//! - update atomicity is suspect: patch application must either
-//! completely succeed or leave on-disk segments intact. unapplied
-//! patches can be discarded (triggering event replay), but once
-//! patch application begins it must succeed.
-//! may require integration into the overall signal-handling regime.
+//! system page size.
+//! - update atomicity is crucial:
+//! - patch application must either completely succeed or
+//! leave on-disk segments (memory image) intact.
+//! - unapplied patches can be discarded (triggering event replay),
+//! but once patch application begins it must succeed.
+//! - may require integration into the overall signal-handling regime.
//! - many errors are handled with assertions.
//!
//! ### enhancements
