Assuming Drupal 7 here, which thankfully has more options for you that Drupal 6.
I don't recall the last time I fully traced this out (and it's complicated), but search_excerpt does call strip_tags and check_plain.
You can take a look at search-result.tpl.php, template_preprocess_search_result(), hook_node_search_result() to see what your options are.
Personally, I would build up my own entries in
$variables in the preprocess, and display them in the template. One option is to make a custom node view for the search results, uild it up with the UI, and then use this,something like:
function mytheme_preprocess_search_result (&$variables)
$result = $variables['result'];
$node = $result['node']; // not 100% positive that this is the right place in D7
$variables['my_custom_search_result_view'] = node_view($node,
and then use
$my_custom_search_result_view in search-result.tpl.php.
Not a full solution for you, but it should be a decent start.