If he doesn't do this, assholes from Sayian Island and other websites take the scans without giving him credit and I don't see whats the problem.
What difference does that make? They're magazine scans and the amount of e-peen over game news has a smaller window of relevance than say, manga scans that've been cleaned and levelled and all that jazz people really make asses of themselves "protecting" from asshole aggregators like NOEZ. Hardly anyone is going to come here to look for the scans, and hardly anyone is going to post here after seeing the URLs (I have an account from years ago).
I hate watermarking in general, but putting it in one place (like a corner) on each scan instead of all over everything is much more polite. If some dick head is going to "steal" the scans and photoshop out the one watermark, they probably would've done it anyway no matter what you try.
So please think before you decide to watermark every little thing, especially in a distracting way. I like JJBA a lot and that's all I came here to say.