There may be a way to set the actual comment with an
add-in...
But you could create a custom variable for the comment put a field
on your data cards to show that comment, then you can use
transition actions to set the variable and that'll update it on the
card.
Looks like you're going to be stuck learning how to do
add-ins.... lol.... seems as though you can do it with an add-in:
IEdmHistoryUpdate::UpdateVersionComment
Call this method to update a version comment. The actual update is
not performed until you call the CommitUpdates method.
IEdmHistoryUpdate::UpdateRevisionComment
Updates the comment of a revision. The update will not actually be
written to the database until the CommitUpdates method is called.
But you could create a custom variable for the comment put a field on your data cards to show that comment, then you can use transition actions to set the variable and that'll update it on the card.