Hi Peter,
Good testing idea. Here are the results which I hope will help you:
Using the Search UI, I set the four fields to:
Title
Contents
Author
Keywords
The Select was set to Contains, with the same Search Term set for all 4 fields, and the Combination set to OR:
This search yielded good results.
Then, on the last Field, I changed the value from Keywords to Remarks and got NOTHING.
Then, I changed the last field from Remarks to Original filename and also got NOTHING.
Rob Ralston