Base58 was chosen not for human readability but to make it easy to copy/paste.

It was also chosen for hand-writeability, weirdly enough. That's why it excludes some confusible characters. But Satoshi didn't really understand how people would end up using Bitcoin, he originally imagined most transactions being done directly between pairs of IP addresses.

Copy/paste of HTML content is currently not possible. You *can* already drag&drop the bitcoin: link to the client. Bluematt has a pull request to automatically handle bitcoin: URLs when clicked in the browser.

That's cool. I hope Matts change gets merged soon. Then the issue becomes how do people find out about this capability? Expecting people to learn how to hand-craft Bitcoin links won't work. But all modern operating systems support copy/paste and drag/drop of rich content. Qt probably makes it easy to expose an UI like this:

Pay me [Copy to clipboard]

Clicking the link in the UI would pop up an alert saying something like

"You can drag this link to an email, chat window or editing program."

Dragging it/pushing the copy button would just set the drag/clipboard data as a bit of text/html content. So then you can just copy/paste into an email or HTML editor. It wouldn't work for forums that use bbCode, though I guess there's no particular reason the forum software can't turn <a href> into [url=] automatically.