I completely agree. I'm finishing the (HOPEFULLY!!!) final editing stages of my first novel, and it's hard not to let outside influences in. I try to filter what I think would benefit my writing from what will obstruct it, but it's a challenging process. I find now, having other people read and help me edit my book, there are certain things I am very loathe to change, because they seem like aspects that are important to shaping my characters they way I want them to be and thus moving the plot in the direction I want it to go.
At this point, they are like real people to me, and I feel I know them and know how they want to behave, and that's how the plot moves along;-) It's a process, I suppose. Do you find it gets easier as you gain experience?

I, too, agree with you.
I applaud originality in an author. But I also don't accept originality as an excuse for bad writing. I stopped reading a particular author because they seemed to let the ever-growing popularity of their series' main character dictate how they write him/her; i.e. The success seemed to get into the author's head and the author started dressing like and living like the main character. (A bit egocentric and too weird for me!) That's an extreme case, however, I'm sure it's extremely hard to keep the delicate balance without being influenced somewhere in the process of creating. I love characters that evolve, change with their circumstances. I also applaud the author for making hard choices, i.e. killing off a beloved character, IF that is the natural course of the storyline.
Criticism, if meant to be thoughtful and objective, is a good thing. But an author writing voice should hold onto his/her convictions on how they want their story to unfold, especially in a series.