Should tracing headers be included in 304 Not Modified responses?

I could not find any information about this. But my understanding is that any header included back to the client in the 304 Not Modified response gets merged with headers of the cached resource. This means that if I return tracing headers based on the new request they will get merged back with the original request's response, overriding those tracing headers there. Is there any guideline if tracing headers should be issued or not in 304 Not Modified response?

I see the options:

• If they are issued, then they override the original tracing headers, so now the cached response looks like it was made by a new request. Which might be confusing because the new request might have exited early (because it could return 304 Not Modified) so the content of the original response and tracing headers of the new response might be inconsistent.
• If tracing headers are not issued, then all information helped with tracing debugging 304 Not Modified response might be lost.

Start with issue #554 and review its 14-comment thread; no files, tests, or entry points are named in the payload. Done would require an agreed guideline for whether tracing headers belong in 304 Not Modified responses and documentation of that decision.