I tried the basic copy and paste-myspace to comcast-but it just leaves the site without the highlighted link for people click.
When you are composing an email in Apple's Mail.app email program, if you paste in a full URL, including the http:// at the beginning, it will work as a clickable link in the email you send. However, it will not be clickable in the window where you compose the email, only in the email that your recipient recieves.
Test it. Type a full URL into an email in Mail.app, for example:
It won't appear to be clickable in that composing window. But send that email to yourself. You'll see that in the email you receive, that link will be clickable.
Note: This is somewhat dependent on the email program your recipient is using. Some will block links from being clickable. That's not something you can control. But most email programs will allow it to be a clickable link.