diff --git a/docs/STYLE b/docs/STYLE
index 60f306a33..38db980f1 100644
--- a/docs/STYLE
+++ b/docs/STYLE
@@ -57,9 +57,14 @@ Whenever joining more than two strings, use string interpolation, not addition:
 This has to do with efficiency; the intermediate string x+y is made (and thus
 copied) before x+y+z is made, so it's less efficient.
 
+When writing strings that have formatting characters in them, don't
+use anything but %s unless you absolutely must.  In particular, %d
+should never be used, it's less general than %s and serves no useful
+purpose.
+
 Use the debug module to its fullest; when you need to print some values to
 debug, use debug.printf to do so, and leave those print statements in the code
-(perhaps commented out) so they can later be re-enabled.  Remember that once
+(commented out) so they can later be re-enabled.  Remember that once
 code is buggy, it tends to have more bugs, and you'll probably need those print
 statements again.