As you know, Bitcointalk doesn't have resizing buttons available when you create new posts.
I'm aware there is no specific button for resizing, but entering a text into the image tags would adjust the image sized, such as what k used in the image linked above:
[img [b]height=120[/b]]https://i.imgur.com/Fssg7Uo.jpg[/img][hr]
Not sure if it's what you're referring to.
On bitcointalk, even if you prove image plagiarism, and plagiarist admits it, he still won't get banned
It could be the mods prefer not to interfere in image plagiarism as it's a grey area, so they rather avoid making a decision. It would be better to hear directly from a mod, if it's a ban-able offense.