Real street togs would never think of corrupting a moment they are about to capture by intervention, this could be staging a moment, introducing flash or using props. The problem I have with this statement is that it ignores one vital aspect and that is that sometimes the photographer is part of the moment and through shadows or reflections can actually become part of the work.
I have seen images presented which include togs using flash through cafe and bar windows which are supported by words of justification arguing that the photographer and the flashgun are part of the moment, a huge highlight in the centre of a piece is just plain bad photography especially when the highlight was caused by an artificial light source introduced to the scene by the photographer.
As a "old Skool" photographer most of the time I try to eliminate my presence from the scene I am trying to capture but this principle was challenged recently when I was separated from a subject I wanted to capture by a huge plate glass window. I discovered that if I included my own reflection in the scene the subject became clearly visible and in fact with a little care could be made to appear as if his head was attached to my silhouette. This is the first time i have ever used my presence as a pictorial element in a photograph other than the humble selfie's I take now and then and have to admit to being pleased with the outcome.
As a rule I still prefer not to influence the images I make with tell tale signs of my presence but now and then it might be okay to take a lesson from Alfred Hitchcock and make a cameo appearance in the works I make.
Keep it real !