Jeff, 
thanks for the pointers. I see your point about stemming not working:
Thus a search for "silent" will not match an indexed word "silently"
like it should when stemming is used. 

Maybe this issue needs to be clarified to come up with examples
that we could fix. I see two classes of problems:

a) exact matching of words does not happen like it should with 
Xapian. (I believe this is what Thomas wanted to report about.)

b) matching stemmed word does not work, like it should with Xapian
and using its stemmer.

My point is that a) is not affected by the upper case stemming defect
as this will happen with all words and thus the exact match works.
(I tested this.)

Maybe we should open another issue about b)?
What I am sure about is that we should also file this with Xapian,
I guess they should add documentation to their API reference that 
stemmers are only to supposed to work with lower case, e.g. here  
http://xapian.org/docs/apidoc/html/classXapian_1_1Stem.html#e4b7a74ac5bd468beb4e6c55d776fba0
Otherwise it would be a defect.