It supports fairly full featured, hierarchical to do lists. However, it also has a rich text component for its comments, that supports the features you describe. I use that component for quickie logs; Control-D inserts a timestamp at the insertion point.
Again, I realize it doesn't precisely fit your description, but on the chance you or another reader finds it of interest.
http://www.codeproject.com/KB/applications/todolist2.aspx
It supports fairly full featured, hierarchical to do lists. However, it also has a rich text component for its comments, that supports the features you describe. I use that component for quickie logs; Control-D inserts a timestamp at the insertion point.
Again, I realize it doesn't precisely fit your description, but on the chance you or another reader finds it of interest.