Why are there so many messages in the changeset history for a rarely changed area?

ITO's OSM Mapper application also allows you to "watch" an area in a similar way to OWL. Like OWL, it only shows actual changes with the area that you're interested in, not those that have a huge bounding box that incorporates it.

It doesn't yet track deletes though, so it won't find who deleted some stuff of yours unless the person that did it also added something new.

Note at the moment the OWL service seems some what defunct.

There is a new 'service' that goes some way to remove massive bounding box changes that cover the area in question, working from the basic OSM history feed.

http://positron96.appspot.com/osmfilter.html

Hopefully one day OWL will come back and be part of the core OSM services.

If you mapped in the area, you can then identify the changesets that you created and then find the nodes, ways etc that you created. You can then look at thier history and see if they have been changed, moved or deleted by someone else since you created them.
Use the link to 'Your user page' and the 'my edits' link to do this. Paging through your edits may find your changeset if you know when the changes were made or have a helpfull comment. If you don't know when the change was made but can identify the area, adding a bounding box to the search may help. So for the link you provided try the following

In the Potlach2 editor it's easy to find who as worked on a way.

1. Enter edit mode
2. Highlight way
3. Click on advanced tab (bottom of tagging box)
4. Click on way number (top on tagging box)
5. You should now see edit history of that way
6. Highlight one from list
7. Click see more details

Hope this helps