H Brian,
I would suggest to try and apply the Number format without comma separator to the Universe Object Year at universe layer, so that it resolves problem once for all across multiple reports. I think, It should work fine retaining the format given to the universe object across reports, provided you uncheck "Regional formatting settings" in document properties.
Right Click on Year Object in Universe>Object Format or Edit Format and assign the number format without comma separator there, save business layer and publish it.
Thanks
Mallik