<a href="index_html">index_html</a> got transformed to

<a href="index<u>html">index</u>html</a>
(reported by Amos)

lib/python/StructuredText/STletters.py

@@ -12,6 +12,6 @@ letters     = string.letters
 literal_punc = punc_func("'")
 dbl_quoted_punc = punc_func("\"")
 strongem_punc = punc_func('*')
-under_punc = punc_func('_')
+under_punc = punc_func('_<>')
 phrase_delimiters = r'\s\.\,\?\/\!\&\(\)'