Agreed, I will see that we fix that.
Opinions vary, if the field is really simple it can be OK, but I agree that having the help text disappear when you type in the field is kind of a worst case scenario. As you type is when you need the help the most...
Agreed we need to do this as well.
Another great idea. Will look into this.
Doesn't matter, if they forget their password to any of those, and they will... guess how they recover the password? Email is the bedrock of social Internet, nobody will ever kill it.
Repeating the password is user hostile at this point, will reduce sign ups, and just isn't that effective. Better to have simple fast password recovery. Most sites are moving away from this "must repeat password twice" design and I agree with that.
Also @darrenpmeyer and others, this idea that an attacker can now mine your login form for emails is kind of an illusion; you could do the very same thing with the signup form, where you must tell the user if that email exists or not... That said, if you want this feature it can be turned on in the site settings in Discourse.