I've been directed to create a bug report, after I reported this issue in the forums:
http://forum.dokuwiki.org/thread/7527
What happens is that whenever I add a word in the wiki that contains Capital Letters, the index file stores the case sensitive version of the word, as it appears on the page, rather than converting the word to lowercases and storing that in the index.
For example, if I have two pages, one which contains the word "CapitalizationDoesNotWork" and the other the word "capitalizationdoesnotwork", the w25.idx file will look like this
capitalizationdoesnotwork
CapitalizationDoesNotWork
Searching then for the word (capitals or not does not matter), will return only pages containing the lowercase versions.
Also, if I add a word with Capital Letters but then modify the index file manually to be in lowercase, the word will be findable via search, even if the actual word on the page contains Capitals. In the same vein, if I put the same word in the same page twice, but one containing capitals, the search functionality *will* find both versions.
I am running Rincewind stable on Solaris 10 on Sparc on apache2
SunOS hostname 5.10 Generic_127111-06 sun4u sparc SUNW,Sun-Fire-V440
# /usr/local/apache2/bin/apachectl -v
Server version: Apache/2.0.59