There is a big difference between annotations and a comments.
Sometimes, I just want to comment on a page or cell or a specific part of the content. This is more an annotation. It contains important information, but there is no action required.
Comments as they are currently implemented in Coda are more a conversation and need to be resolved. This may be the most frequent use case.
Anyhow, I also would like to be able to add annotations to a coda page or cell in a table.