Questions are often the strongest way to end your discussant comments. Develop questions for either the authors or the audience or both. Both experienced researchers as well as new Professionals often find themselves struggling in their role as discussant. There are many different reasons why people feel conflict over their role. Below are a list of common problems as well as some helpful hints for addressing them.
Papers are late.
Tactfully acknowledge the paper came in late. This is important for the accountability to all your colleagues. Note that, unfortunately, this is why you do not have typed feedback for this author. This helps the author know that they missed out on important feedback. But, tell them that you have some less extensive comments to help the audience in their critique as well as a few synthetic comments to tie the papers together.