Regarding Opeth's influence on PT, I have also found that Wedding Nails really reminds me of Opeth, specifically the end of Deliverance the song.
The funny thing is that no matter how much people either like or dislike the Wilson influence (which I like), BWP is a more straightforward album in terms of metal than is Still Life. And no matter what Ghost Reveries sounds like in some songs, I do not think that (Damnation notwithstanding) Opeth will ever record an album that feels as rock oriented as Still Life. The riffs in Moonlapse Vertigo are just some great rock riffs with Opethian arrangements.
I just wanted to point out two things really I guess: First, the two heavy Wilson albums are to me, well, more metal than rock oriented, in contrast to where I thought they were going with Still Life. And if you go from BWP to Deliverance, then it's progressively heavier (and subtle, using texture and atmosphere more than 12 million layers, which is both more musically straightforward and more challenging). To me this means that either maybe, and I know this might be hard to think about, Mike and not Steven really is in charge of the band's sound and songwriting. The other option is... well no, I think that's what it means.
The other thing I wanted to point out is that I think that if you put me in a room with the Opeth catalogue, which I had never heard, started me with Still Life and said Steven Wilson of PT produced the next album and had a big influence on it, figure out which album he produced, I would select Ghost Reveries over BWP without question, because it containes more of the rock vibe (most notably in the softer songs) that I got from Still Life, whereas BWP just feels more like metal than rock to me.
Say what you want, but I think that PT took a lot more from Opeth than vice versa, perhaps b/c Mike already listened to PT, but Steven Wilson didn't listen to Opeth beforehand. Wilson's influence was present in Opeth long before BWP, it's more production choices (and yes, the ever-present mellotron) than he imparted to Opeth, whereas In Absentia and Deadwing reek of Akerfeldt in places, whether it's from the big, heavy riffs, or even some of the chordal changes and atmospheres/emotions of songs like gravity eyelids.