Having read the two/three star reviews, it seems as though certain people weren't paying enough attention throughout the film, so to clarify then:
No one recognises Chen Zhen because it clearly states at the start that Shanghai has been divided into settlements pending an invasion. He's also trying to infiltrate the Chinese Triad/mob in order to win their allegiance. Do I have to point out that as The Masked Warrior he's wearing, gasp, an actual mask? Besides, Clark Kent only fools people with a pair of spectacles.
The reason he's part of the Chinese resistance is in order to unify the Chinese patriots (and student protestors) against their aggressors. This is made abundantly clear throughout several meetings of the resistance. Chen's one man who can make a difference and rally people to his cause. Hence, he plays the role of a spy with a fake identity.
The Japanese Colonel already knew that Chen was responsible for his father's death. He wanted vengeance, whereas Chen was fighting for justice. By this point in the film, wearing a mask would have been counter-productive, especially for a one on one duel. As for any Bruce Lee comparisons, why shouldn't Donnie Yen pay homage to someone he respects and admires? It's a different time period, so any grumblings are purely superficial AND irrelevant. Side note: if utilising a set of nun-chuks is 'fighting like Bruce Lee' then what isn't?
The nightclub owner (Mister Lau) befriended Chen Zhen after he played a raucous Chinese song to grate several Japanese military officers. Mister Lau saw him as a kindred spirit (someone who despised the Japanese) and a beneficial partner in the running of his nightclub. Not to mention that in order to keep peace he told the Colonel he'd close Casablanca, if he was able to open his own nightclub.
The story is not a mess, at least not as much as other reviewers would have you believe. There are strong characters, a rich score, brilliant set-design, and breath taking action scenes/fight sequences. The opening sequence and library sequence have to be seen to be believed. As for dodgy CGI, um, at which point exactly? The making of bonus clearly shows Donnie performing ALL his OWN stunt work with no CGI involved. Kudos to a man who can effortlessly jump over a Bentley and still land on his feet. As for the opening 'clearing a building full of german soldiers scene' - well, actually, it was a german mini-gunner and about half a dozen soldiers.