Wikitech,
It's mentioned in the ''Tatabahasa Bugis'' book or Buginese grammar
published by ''Departemen Pendidikan dan Kebudayaan, Indonesia'' (The
Indonesian department of Education and Culture.) If you can read
Indonesian, I can scan it for you.
Likewise, as mentioned in the Andi Mallerangeng bugis font page, the first
to create this software-font, he used underline to replace this diacritic.
Here's the page:
<http://www.seasite.niu.edu/bugis2.gif>
Thank you,
Muhammad Zaid Zainuddin