The scenario:
On the comment listing page, there is a "Show Display Options" setting at the bottom of the page. I received a notice from my hosting service that my site was approaching its size limit. I went in to clean up the junk comments*, and discovered there were tens of thousands of them. I used the "Show Display Options" settings to show ALL of the junk comments so that I could delete them all at once. Other than taking quite a while to display the comments and moving slowly when deleting them(obviously), this worked fine and did not cause any problems.
The problem appeared to me after the delete was finished. I was returned to the Junk Comments page and saw the notification that "No junk comments could be found." (Yay!) However, at this point, I did not have the "Show Display Options" link, so I could not change my setting back to a lower number. Instead, I had to switch to the view of my comments, which brought up ALL comments and therefore again took a long time to load. At that point I was able to use the display options link to change the setting back to something more reasonable.
So, this is not a bug or anything, but I thought it might be possible to rather easily address that behavior in a future release. It would be great to be able to get back to that "no junk comments could be found" page and still have the ability to change the display options from there. If that is not possible, I would suggest saving those display options separately for the regular and junk comments. The first option strikes me as the more feasible one, but of course there is a reason that YOU code this application and not me.
Anyway, just wanted to share the thoughts.
*Note: I have since changed the default cleanup to a much shorter time span.