How do I upload a photo from my computer when commenting on a blog post?

Hiya,

I've just realised that when commenting on a post, the image uploader requires a url rather than allowing you to select from your computer (when you initially create a blog post, you have the option to do either). I have the same editor displayed as the one used in this support forum... without the panel below (attachments, polls etc).

How can I attach a picture to a comment on a blog post, please?

Thanks!