Hi!
Indeed, it is not yet possible within the current release, but it will be in the upcoming one. Instead of going through the results templating, I would rather suggest a modification to one of the template files, which will resolve the issue, and allow HTML tags in that field. It will be included in the upcoming release as well, so you won’t have to worry about that either.
To resolve that for now, you only need to replace one of the files on your server:
1. Before starging, make sure to have a back-up copy of everything.
2. Replace the wp-content/plugins/ajax-search-pro/includes/views/results/no-results.php file contents with this
3. Save and reload the search options page.
Now entering HTML should be processed correctly in the ‘no results’ text box.
Let me know if you need assistance with it.