Updated SC2181 (markdown)

SC2181-tell-inverting-return-value-will-overwrite-it.md

@@ -33,7 +33,7 @@ Apart from the redundancy, there are other reasons to avoid this pattern:
 
 To check that a command returns success, use `if mycommand; then ...`.
 
-To check that a command returns failure, use `if ! mycommand; then ...`.
+To check that a command returns failure, use `if ! mycommand; then ...`. Notice that `!` will overwrite `$?` value.
 
 To additionally capture output with command substitution: `if output=$(mycommand); then ...`