GitHub Pages announced the discontinuation of support for Textile in Jekyll sites starting May 1st, 2016, urging users to convert their sites to Markdown. The transition involves either manually editing a few Textile pages or using tools like pandoc for bulk conversion, with a specific script called tomd designed to handle some of pandoc's limitations. The manual conversion involves changing syntax for elements such as headings, links, and lists, while the automated method requires installing pandoc and tomd, which can convert .textile files to .md and store backups. The conversion process may still present issues like lost CSS references and mixed HTML/Textile formatting, and Windows users will need additional utilities like cygwin to execute the script effectively.