I noticed that comments to questions or answers just disappear and it seems to me that the user whose comment is removed does not get an information or explanation about that.
Is this normal?
Is this volitional?
It's perfectly ok that the moderators invest a lot of time and effort in the coherent structure and content of this site.
However it would be IMHO useful for the users whose contributions are changed or removed to be aware of what happened and why
- to know what they have "done wrong" (maybe violated the netiquette)
- and to get a change to do it better next time.
This is often the case but not always.