TsumegoFromGames63/Evolution-Explanation

Tsuke-hiki 6-8 is agood move  

tderz: the hiki of the tsuke-hiki combination - was a good shape move.

Vulgar atari changes the outcome  

tderz: After the vulgar atari ,
Black must come back in gote and defend the cutting point a.
This gives White just enough tempo to save her group with b + c ("6 on the 2nd line in the corner lives").

Why is so vulgar, so bad? (in comparision to above )

• First, as explained, it loses a tempo.
  
• Secondly (of course linked) it removes a weakness of White:

Removal of white weakness

tderz: is a weak spot in White's formation:
Black can peep there and has the miai pairs a-b and c-d to kill.

Right: The weakness has been removed (it's white's turn on the right side)