if you 'undo remove' a smart parameter, its content is added to all other parameters content.

to replicate:
1) edit a puppet class
2) click on smart class parameter tab
3) select a parameter (capture1.png)
4) delete it by clicking the respective 'x' in the parameter list (capture2.png)
5) select any other parameter (capture3.png)
5) click 'undo remove'
6) the two parameters you selected will now have the same (removed parameter) content (capture4.png)
7) all other parameters will have the removed field content appended/prepended to them (capture5.png, capture6.png, capture7.png)