define(FOO, t("bar")) is a performance disaster.

Any time you try to translate something before the bootstrap is finished it rebuilds the entire cache of localized strings. Thus, non-English sites with this module have to build the entire cache every page load resulting in an extra query for every string, every page load (yes, this is how I've seen sites have 14,000 queries, every page).

Can't roll a patch right now, but here is what needs to be changed:

diff -u -r1.15 commentmail.module
--- commentmail.module	22 Jun 2008 15:56:23 -0000	1.15
+++ commentmail.module	4 Oct 2008 10:02:15 -0000
@@ -6,7 +6,7 @@
  *   - integrate with token module
  */
 
-define('COMMENTMAIL_DEFAULT_APPROVE', t("An unapproved comment has been posted on @site for the post '@node'. You need to publish this comment before it will appear on your site.
+define('COMMENTMAIL_DEFAULT_APPROVE', "An unapproved comment has been posted on @site for the post '@node'. You need to publish this comment before it will appear on your site.
 
 approve/edit/delete/ban: @quick_approve
 
@@ -19,9 +19,9 @@
 
 approve/edit/delete/ban: @quick_approve
 
-Comment administration: @admin_url"));
+Comment administration: @admin_url");
 
-define('COMMENTMAIL_DEFAULT_NOTIFY', t("A new comment has been posted on @site for the post '@node'.
+define('COMMENTMAIL_DEFAULT_NOTIFY', "A new comment has been posted on @site for the post '@node'.
 
 THIS COMMENT DOES NOT REQUIRE APPROVAL
 
@@ -34,7 +34,7 @@
 
 edit/delete/ban: @quick_approve
 
-Comment administration: @admin_url"));
+Comment administration: @admin_url");
 
 
 /**

Note that you already translate the constants later in the code, so the strings are being double translated.