How do I quote multiple parts of an email?

In Mail, while viewing the message select Reply.

Click at the end of the first item that you want to respond to.

Press return.

Type your response.

Click at the end of the next item that you want to respond to.

Press return.

Type your response.

Repeat above as many times as you need.

Tacky? It shows up as quoted text and it is extremely easy to use. It is the same way that Thunderbird does it.

How do other email clients do it? What were you expecting?

The ">" has been used for years to indicate quoted text in non-html editors and non-html messages.

Now the editors usually use a vertical bar "|" and indentation to indicate quoted text in html messages. This is pretty common. This is how Mail, Thunderbird, and on-line Gmail and iCloud editors do it.