I was testing sending an email with a read receipt with a webmail client to a Delta Chat account, the message was received and read, but no read receipt was sent back to the other account, also messages sent from within Delta Chat don’t request to send a read receipt when opened in the webmail client.
At former versions of DC there was a user setting for doing that. But as many read receipts are not build according related RFC there is a technical problem in handling.
Now only read receipts with DC generated messages are handled and generated.
No idea if this will be introduced again, maybe with a different approach?