As it stands now, there is no way for an admin to comment on a suggestion while it’s locked. This means that if a suggestion is being flooded with off topic remarks or similar, you either a.) have to send your reasoning BEFORE locking the suggestion, or b.) have to send your reasoning AFTER unlocking the suggestion. I think it would be beneficial for users to be able to lock the suggestion and then be able to send their reasoning for doing so afterwards.
Another twist on this idea would be the ability to include a message while locking the suggestion, that way you don’t have to put more than one comment on the suggestion.