Marking your photos won't stop anyone from stealing them,
no.
A friend suggested that one should mark photos not so much for
protection, but just so that people know where they saw it.
Made sense to me, so I mark mine.
I don't like text going across my pictures, either, so I have
been using a watermark in the bottom corner.
I'm thinking of experimenting with a true watermark diag across.
Yeah, a professional could remove it, an amateur just sharing a
pretty picture wouldn't bother.
I think it's a bit more serious for artists and their original
work, though. Yes, I would use a proper watermark in that
case.