It doesn't seem to be case sensitive to me. Remember you have to take into concideration the spacing and control codes.
/window @test
/aline @test test motd
/aline @test motd test
//echo $fline(@test,*MOTD*,0) returns 2 (total number of matching lines)
//echo $fline(@test,*motd*,0) returns 2 (total number of matching lines)
If you want case sensitive search you could use a regular expression.
