For the record, here's how I created this test repository:

hg init annotate
cd annotate
echo hello > hello.txt
hg ci -A -m'init'
echo world >> hello.txt 
hg ci -m'change on branch (will not merge)'
hg up 0
echo world >> hello.txt
hg ci -m'duplicate change from branch (not a merge)'
sed -i -e 's/hello/goodbye/' hello.txt 
hg ci -m"unrelated change"