diff --git a/doc/todo/enable_arbitrary_markup_for_directives.mdwn b/doc/todo/enable_arbitrary_markup_for_directives.mdwn
index 94713838e..aa7b6fa49 100644
--- a/doc/todo/enable_arbitrary_markup_for_directives.mdwn
+++ b/doc/todo/enable_arbitrary_markup_for_directives.mdwn
@@ -17,3 +17,19 @@ This could also make it easier to support more styles of markup, rather than hav
 -- [[KathrynAndersen]]
 
 [[!taglink wishlist]]
+
+> Arbitrary text transformations can already be done via the filter and
+> sanitize hooks. That's how the smiley and typography plugins do their
+> thing.
+> 
+> AFAICS, the only benefit to having a regexp-based-hook interface is less
+> overhead in passing page content into the hooks. But that overhead is a
+> small amount of the total render time.
+>
+> Also, I notice that smiley does such complicated things in its sanitize
+> hook (ie, it looks at html context around the smilies) that a simple
+> matching regexp would not be sufficient. Furthermore, typography needs to
+> pass the page content into the library it uses, which does not expose
+> regexps to match on. So ikiwiki's more general filtering interface seems
+> to allow both of these to do things that could not be done with the
+> PmWiki interface. --[[Joey]]