Currently, syntax highlighting assumes # is the comment character used in Git Commit messages. The comment character used in Git Commit messages can be configured using core.commentChar in .gitconfig. That functionality is commonly used to change the comment character to something else such that an issue tracker number can be used at the beginning of the commit message such as: #123: Some changes.
If possible, the syntax highlighting would read the configuration to determine the comment character instead of assuming # and highlight comments based on the configured character.