On first reading of the comments here, I was unclear on to what you and Veronica refer – but quickly see that Google in its Alerts lists:

“Brief, non-spoilery review of ‘Watchmen’ – Veronica Belmont
By Veronica
I agree the ‘Hallelujah’ sex scene was a bit long, but it was uncomfortable intentionally. It was supposed to call attention to the absurdity of Dan’s condition, that he has to put on a goofy costume and be Nite Owl to get it up. … ”

And, indeed, on visiting that blog it turns out those words are the comment of someone with the handle Avrithor (and not penned by the blog’s owner).

There’s a number of thoughtful comments, with all range of perspective, on that blog. This #39 post excerpt from Dagsly touches on a theme about which I’ve speculated (not having seen the movie):

“I felt the sex scene between Dan and Laurie was not overdone and needed to be included. I find it interesting how uncomfortable people have become at viewing sex scenes (or even a flaccid blue penis) in theaters. I think it’s possible that the ubiquity of internet porn has trained people to view sex scenes and nudity as something that needs to be experienced alone. Kind of funny really, since communally was for so long the only way people were able to experience sex scenes on film, even non-explicit ones. Makes me wonder if a film like Basic Instinct or Last Tango in Paris could even be releasable today. There’s also the obvious paradox that a flaccid blue penis is considered yucky but repeated cleaver to head and arms chopped off with angle grinder barely register a mention. Makes you wonder about even more about the films commentary on human nature.”

I drove by our local cinema tonight, and “Milk” and “Doubt” have just arrived. It’ll be weeks before there’s opportunity to view “The Watchmen”. Until then, I can’t imagine how I’ll feel about things in the movie, or, how to answer what difference, if any, there’d be had Allison’s recording of “Hallelujah” remained the soundtrack to that distinctly controversial scene.