Here's another solution to this (aside from undoing allowing mods to post to locked topics): when mods post to locked topics, don't put their posts through moderation even if the topic is also moderated. Then the lack of the icon wouldn't matter. I actually don't know what the purpose is of moderating mod posts to locked topics that also happen to be moderated. I only figured out that's what was happening as a potential solution to Bruce's problem of the wayward mods.
So the way I see it, there are three solutions:
1. Do away with the ability of mods to post to locked topics.
2. Keep mod ability to post to locked topics, but if the topic is also moderated, display both icons.
3. Keep mod ability fo post to locked topics and don't moderate their posts even if the topic is also moderated.
Messages are the sole opinion of the author, especially the fishy ones.