@abio33
I do not know what exactly you are tying to accomplish, so I will break this down.
1) Scanlators (with exception to upstarts) have at least 1 person who LIVES inside an image editor program. If they want a watermark. There will be a watermark. It takes no effort to add it.
If they want to remove it, it only takes only a click of a button/layer to disable it and a couple minutes to re-upload.
2) Its ugly. We don't want to read manga with watermarks randomly placed on the image. When scanlators do it manually, they put it in places more discreet and visually appealing, but a site function would not be able to do that. The watermark would be in places that ruin images and make reading unbearable. It would drive readers away from the series and groups that enable the option. (if you do make it small enough to not be obtrusive, you eliminated the only purpose I can think of for having the watermark to begin with. Additionaly, you need to wory about full page images and longstip comics like manhaw)
3) Its now too much of an edge case. The number of people who would want to enable this feature are very low. There are several who want to promote the site, and they do so by adding MD into their credit page, in page margins (where the page number usually is), and other discreet locations.
Adding these takes virtually no time at all compared to cleaning, redrawing, translating, and typesetting the manga. And would look 1000x better than anything we could possibly do. In other words, only really lazy scanlators, or those with 0 image editing experience would want to do this. When it comes to groups with more than a week of experience, thats almost no one.
I should probably have lead with this:
MD rule 3.2.4 Obtrusive watermarks are not allowed.
