Dr. Nic has introduced a new feature in his GitHub Textmate bundle that allows for line commenting, enhancing the ability to comment or discuss specific lines of code directly via GitHub. A demonstration of this feature is available in a video titled "TextMate + GitHub – how to comment/discuss on a line via GitHub from Dr Nic" on Vimeo. Additionally, there is a VIM plugin available for this functionality, which was highlighted by Chris Wanstrath, also known as @defunkt.