The current 200-character limit is far too short. For example the default undo message is 90 chars plus three times the username plus the section name; this can easily take up the available space in itself, and one would often want to write an undo reason too. As page histories are getting longer, reverts more frequent and (with the focus being shifted to quality) history-analyzing tools more widespread, it is important to include as much information into the summary as possible and not force users to delete eg. which revision they have reverted so they can fit in the reason. The max length should be at least the double of the current size.