Say $X$ posts an incorrect, or at least incomplete, answer. I post a complete answer. X edits his or her answer - the new version is imo essentially the same as mine, although imo much less well motivated, with the concepts obscured by magical calculations. (For example...)
Even if X doesn't see how the two answers are essentially the same, wouldn't it seem proper for him or her to at least acknowledge that he or she didn't find his or her answer until after reading mine?
Not important, just irritating. If one looks at the time stamps and ignores the edit history it look like X gave the first correct answer, which isn't so.
(Regarding whether X's answer is really the same, or at least derivative: One might note that there was nothing inner-productish in X's first version. More specifically, using the union of the notation in the two answers, the reason his calculation $||f-f_1||=0$ succeeds is that $||f||^2=|\alpha|^2+|\beta|^2$ and $g\perp b_1$, $g\perp b_2$.)