You seem confused. Signing up to multiple mailing lists won’t require you to have multiple email addresses, and at the same time they don’t require you to subscribe using your main email address either. Many email hosts will give you as many mailboxes as you like, either using plus–addresses or just new mailbox names.
> And then how do you link to users or messages from your email client?
Every email has a unique message id. Simply include a message id in the body of the email, and your email client should turn it into a link (provided you happen to have that message available). If your email client doesn’t do that, perhaps you need a better email client.
> They are unbrowsable and who likes getting their inbox spammed in order to follow a discussion?
It really sounds like you need a better email client, or you just need to learn how to use the one you have better.