I'm note sure about the EU part, because in Belgium you can mention competitors, e.g. "Darktable aims to fulfil the same need as Lightroom" is absolutely allowed, without problems. There aren't even rules specifically for mentioning competitors, it's about comparisons in general. For example, saying your product is "the best on the market" counts as a comparison, and you'll need proof to back up your statements.
Even a lawsuit without merit would require lawyering up and suck scarce time and energy. Adobe has deep pockets and lawyers on staff. Darktable has volunteers.
I agree. I think never mentioning Lightroom is a way of steering clear of meritorious suits and reduces the likelihood of a frivolous one...since even a frivolous lawsuit could be fatal. Anyway, "here is our cool thing" is probably organizationally healthier than "us against evil corp."
