I apologize if this has been discussed already I haven't been coming into this thread as much lately but theres something I've been wondering about all the hate or at least all the dislike Blackwall gets to me seems to be about him lying about being a warden (at least it comes off that way to me) so I was wondering would he have been better received if he was an actual warden? I personally find him not being a warden interesting and think it adds a lot to him. Again sorry if I'm bringing up something that has been talked about already.
I like that he turned out not to be a warden. One, it confirmed my suspicions as I was playing, so I got an "ah-hah I was right!" moment, which is always fun. Two, if he were a warden, he'd have to either be affected by Coryface just like all the other wardens were, or he'd have to have super special plot powers, which I wouldn't like. Three, as much as I'd have loved a real warden companion along the lines of Duncan or Riordan, I felt it made Blackwall's story more interesting to have the twist.
Blackwall never felt like a Duncan to me, as whenever you asked him questions he diverted or evaded, and he had too much "do the right thing" instead of the "do whatever it takes" that wardens have. If he had seemed like the experienced warden and then turned out to be lying, I might not have liked it as much as I did. As it was, I didn't feel like I was losing an experienced Warden, I felt like a soldier I knew was hiding something finally came clean.
I do think the lying contributes to the Blackwall dislike, but I think it's only one factor. He has a few counts against him in the general fandom world, and it seems like if someone doesn't like him for one thing, they dislike him for something else. I don't pay it much mind anymore, since I love him and that's not gonna change 
Hmm... I'm considering trying the Blackwall romance with my new Lavellan this playthrough, after trying both Solas and Cullen. I'm not sure if I can get past the scene on the battlements, though. I've had my Quizzy's flirt with Blackwall before up until the battlements scene (and his flirting is so awesome in Haven!), but once you get to the battlements scene I have a hard time going past that. He just seems so against a relationship (which, yeah, I can understand why) that I go ahead and agree that it's best to end things. I suppose I shall see what happens this time. I do want to try his romance.
The lines do seem a little how of place when you first get there. I feel like they should've had at least one more flirt leading up to it, or written the lines slightly different. They also should have something notifying people that if they don't take this flirt, that's it, the romance will never happen. I know several people have missed starting the romance, because those lines seemed awkward and it doesn't let you it's now or never.
I rp'd a rogue that had a great heart (even though some of her decisions were beautiful disasters), but she wasn't so noble she was going to sacrifice things she wanted for the inquisition. Especially not at that point. So when he's up on the battlements, and he's suddenly changing his attitude, my girl knew he was just being a silly man, putting her in this "inquisitor-andraste's herald" box, and trying to take the weight of the world on his shoulders when it was completely unnecessary. So then the flirt lines feel much less like 'i won't lose you, we have to start a relationship right now, please be with me!" as it they do, 'hey, i'm not letting you sacrifice yourself for me, that's silly. And I totally see you getting scared of your feelings and trying to run away, and I call you on it."
Basically through the game, he'd be like, "Here, my lady, I've made you this wonderful pedestal to step.... What are you doing with that mud? Oi!" An exhausted, dirty, muddy hour later, "Well, I never imagined a pedestal could have so many uses. I do believe you've broken it, my lady."