Thank you.
I understand that "Content-Disposition: inline" with "multipart/related" reflects the sender's intent for images to appear within the email of the recipient.
Nonetheless, many email clients offer recipients the capability to optionally hide inline images.
Lots of email is unwanted, and sometimes, there are offensive images that are sent inline, so that the reader or people who might be nearby when the message is opened are forced to view those images. Having the option to block inline images is useful to protect against this case.
Luckily, I manage my own email server, and I can write filters to preprocess "multipart/related" messages to convert them to "multipart/alternative".
However, most people cannot control their email servers in this way.
Anyway, I, for one, will be grateful if some day Aquamail offers the capability to optionally hide inline images.