I used to use WP.com. If you insert a thumbnail it will just use img.jpg?w=600. It resizes on the fly.
Now here if you insert it will put img-200x100.jpg or whatever depending on size. If you want to make it bigger you can't, u must reinsert from scratch. If you make it smaller it'll load the big one. It's terrible and no good for portability.
Why is it like this? If it's available for WP.com from 4yrs ago, why can't we have that here too?