What should sop say about compression?

Some sop implementations (like pgpainless-cli 1.6.8) produce output from inline-sign that is wrapped in a compression layer.

The current sop specification doesn't prohibit this, but maybe discourages ingestion of compressed messages, due to some of the packet guidance (see #24 for example).

Should sop be more explicit about the use of compression layers in the artifacts produced or handled?