When a moderator locks a question or answer, they can choose between different types of post notices: content dispute, off-topic comments, historical significance, wiki answer, or no notice. The notice in turn affects the effect of the lock, but that it works this way is not clear to moderators and it is also not clear what effect a given notice has. The only way to find out for sure is to ask somebody who is not a moderator or use a sock. (This is due to moderator powers possibly overriding the effect of locks.)
Store the effects of a lock separately independent of the post notice. In the interface for locking a post, provide moderators with a checklist regarding the effects of the lock, for example:
This lock prevents:
For questions, also add an option to apply the same lock to all answers to the question. For the canned lock reasons, automatically provide an appropriate choice as defaults.
At the very least make it clear in the dialogue what detailed effects a lock has.
Post locks are used rarely, but when they are it is often for important reasons such as avoiding a divide of the community, an escalation of events, or similar. Thus, locks are a tool which moderators have little experience with, but whose correct use (i.e., choosing the right type of effects and knowing what the effects are) may be crucial. Moreover, many locks are used for special cases with individual needs, which in turn require individual locks.
In a specific example, there is a question on Academia, which lead answers and comments, whose appropriateness for the site is subject to a Meta discussion. To avoid further potentially inappropriate comments, answers, etc., I wished to lock question for the remainder of the Meta discussion. I chose content dispute as a lock reason, since it seemed most appropriate notice, however this only prevented edits to the question – which makes sense in other cases but not here. After I noticed this, I chose a historical lock (which I knew to be affecting everything) and removed the post notice (because it was not appropriate). The latter action lead to comments on answers being allowed (because that’s what a lock without notice does for whatever reason), which was not the desired effect either.
Make locking posts more granular – This seems to be partially addressed: The different locks already do have different effects. However, my request goes further than this.
Allow moderators to choose a custom reason for locked posts – This is about customising the notice not the effect.
Can we get a comments only lock? – This would be addressed with this.