Do you think that a strategy developer reflects his/her own personality in the strategy? If so, do you think that's a good or a bad practice?

Yes, every one has his/her stamp in the work which is reflected normally.

I see that personality is reflected in how a person produces the product and not is the product itself. Characteristics of a winning strategy is not related to personalities.

Strategy is basically planning level function and planning is related to the mind skills, so its the Strategy Developer personality that reflects at this level. I would say when it comes to a human mind, it will have its own impact, that is it may have good or bad choice to accept it as a consequence. But obviously a learned Strategist will try to minimize the bad choices.