I created the following dirs and files:
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mkdir /tmp/src
mkdir /tmp/dst
mkdir /tmp/comp
touch /tmp/src/test
touch /tmp/comp/test
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Now, "test" has the same checksum, but different modification time. I use "--checksum" to ignore modification times and it works as expected:
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rsync --recursive --links --perms --times --group --owner --devices --specials --verbose --checksum --dry-run /tmp/src/ /tmp/comp
sending incremental file list
./

sent 79 bytes  received 22 bytes  202.00 bytes/sec
total size is 0  speedup is 0.00 (DRY RUN)
###################################################################


But it does not if I use "--compare-dest":
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rsync --recursive --links --perms --times --group --owner --devices --specials --verbose --checksum --dry-run --compare-dest=/tmp/comp /tmp/src/ /tmp/dst
sending incremental file list
./
test

sent 83 bytes  received 22 bytes  210.00 bytes/sec
total size is 0  speedup is 0.00 (DRY RUN)
###################################################################


This works only, if I disable copying the modification times by removing "--times":
###################################################################
rsync --recursive --links --perms --group --owner --devices --specials --verbose --checksum --dry-run --compare-dest=/tmp/comp /tmp/src/ /tmp/dst
sending incremental file list

sent 73 bytes  received 12 bytes  170.00 bytes/sec
total size is 0  speedup is 0.00 (DRY RUN)
###################################################################


This means "--times" acts like a skip switch if "--compare-dest" is used, which I think is wrong.