This is a small patch against Include.py that allows the 'level' argument to be negative.  When a negative level argument is supplied, the level of titles in the included document is reduced by the specified amount.

For example, given {{{[[Include(MyPage, ,-1)]]}}} a title like {{{= Title =}}} will be changed to {{{== Title ==}}}, {{{== Sub Title ==}}} will become {{{=== Sub Title ===}}} and so on.

{{{
--- Include.py.orig     2007-09-25 08:12:43.000000000 +1000
+++ /usr/local/moin/lib/python2.4/site-packages/MoinMoin/macro/Include.py       2007-09-25 08:46:29.000000000 +1000
@@ -25,7 +25,7 @@
 
 ## keep in sync with TableOfContents macro!
 _arg_heading = r'(?P<heading>,)\s*(|(?P<hquote>[\'"])(?P<htext>.+?)(?P=hquote))'
-_arg_level = r',\s*(?P<level>\d*)'
+_arg_level = r',\s*(?P<level>-?\d*)'
 _arg_from = r'(,\s*from=(?P<fquote>[\'"])(?P<from>.+?)(?P=fquote))?'
 _arg_to = r'(,\s*to=(?P<tquote>[\'"])(?P<to>.+?)(?P=tquote))?'
 _arg_sort = r'(,\s*sort=(?P<sort>(ascending|descending)))?'
@@ -50,6 +50,25 @@
         titles.append((title_text, level))
     return titles
 
+def shrink_titles(body, amount, title_re):
+    position = 0
+    for title, _ in title_re.findall(body):
+        h = title.strip()
+        level = 1
+        while h[level:level+1] == '=': level = level+1
+        depth = min(5,level+amount)
+
+        position = body.find(h, position)
+        newh = h
+        while level < depth:
+            newh = '=' + newh + '='
+            level += 1
+
+        body = body[0:position] + newh + body[position+len(h):]
+        position += len(newh)
+
+    return body 
+
 def execute(macro, text, args_re=re.compile(_args_re_pattern), title_re=re.compile(_title_re, re.M), called_by_toc=0):
     request = macro.request
     _ = request.getText
@@ -112,6 +131,12 @@
         inc_page = Page(request, inc_name, formatter=fmt)
         inc_page._macroInclude_pagelist = this_page._macroInclude_pagelist
 
+        # If level is negative, reduce the size of included titles by that amount
+        if args.group('level') and int(args.group('level')) < 0:
+            body = shrink_titles(inc_page.get_raw_body(), abs(int(args.group('level'))), title_re)
+            inc_page.set_raw_body(body, modified=True)
+
+
         # check for "from" and "to" arguments (allowing partial includes)
         body = inc_page.get_raw_body() + '\n'
         from_pos = 0
}}}

 Great patch, thanks!  Please include in the default Include.py!