When files are checked out, the comments added when the files were checked-in are not displayed in the files. Users checking out the same files can see the check-in comments displayed correctly.
This is a known issue when using a Cache Agent. The Log keyword is not supported by Cache Agent checkouts. If the StarTeam MPX Cache Agent is disabled, the "$log$" keyword will work correctly and the comments will be included.
If the Cache Agent cannot be disabled a workaround is to use the History keyword as a replacement for the Log keyword.