I think there is a huge divide here, which is why you are having trouble parsing this:
On one side of the 
you have users who use “email” as a “trigger” to get them to visit forums.
On the other side you have users who want to do the majority of interaction via email, they do not care that a forum exist, all the want is MAILMAN foreva ™
For the mailman users:
- They do not care about titles and avatars, email is enough, when they see all this duplication they have an internal fit.
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They also do not care about all the emphasis to visit the site, large footers and big blue buttons turn them off.
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They hate the way titles are full of [XXXX] [YYYY] before they see actual title.
I do not see us being able to make both “groups” of users happy out of the box that easily.
What I would prefer to see done here is to provide the extensibility to override these templates.
Where I would recommend starting is with a plugin that allows users to select an email template as “minimal” or something along those lines. Then @LeoMcA can have all the Mailman ninjas 
simply select a different “minimal” template.
I think it is incorrect to look for a solutions that works for two groups that have almost nothing in common. We will just end up making everyone unhappy.