Many people assume I’m christian and become startled when I tell them otherwise. Saying, “ but you’re so nice,” or “how can you be so happy?”
Like my being an athiest makes me a depressed grouch by default.

Nope! Everyone still thinks Im awesome and amazing

No. Not professionally or to anybody who matters to me.

I wouldn't say that, but I do have relatives that say "I know he was raised better than that", and church members that have said to my friends "I don't know how such a good young man got sucked up by the world".

on the contrary, it strengthened my reputation as a rebel.

I live in a small town a little over 500 people in Missouri. All Christians here. They know I am a Atheist. We all get along and respect each other.

I get what you’re asking, but these words partially describe me. They don’t strain my reputation, they are part of it.

Nope !

Everyone knows I do not care about their religion, so they usually do not care about the lack of mine

Well, I'm not sure my reputation has been ruined so much as carefully cultivated in a negative direction. I don't mind the connotation and perceived association so much, because it kind of fits with my general misanthropy. Where I live, despite being a rural community, there doesn't seem to be a lot of backlash for being nonreligious — until we get to personal relationships, like relatives, who are convinced I'm the most extreme godless liberal they've ever encountered.

Not yet... I'm really not out there yet..

It has never stained MY reputation but it possibly has stained another's perception of my reputation.

No, I'm in New York. Not a problem here, thank god!

On the contrary. It embellished it.

A couple of times with family and former friends.

Most of the people who really care about me don't mind that I'm an atheist. Once when dining out with a couple of family members, I remarked that I am not a Christian. They fell silent for a moment, but the conversation quickly resumed and didn't criticize or try to change me. On a number of occasions, I've encountered disapproval here and there, but it hasn't caused any serious harm in my life.

It might, but I don't practice atheistic evangelism. Politically though, I don't accept nonsense and it has better defined who my friends are.

Not yet...that I know of.

After my involvement with a church, I'm sure certain heads would explode if they found out. Like, full-on crisis of confidence moral dilemma time.

Not that the other person showed on their face or mentioned verbally.

If it has, it's not to my knowledge.

Yes, but a little bleach and some mild detergent removed the stain. Accidents do happen.

I'm sure it has, but likely only with close minded folks who have a superiority complex.

I don't wear my disbelief on my sleeve like the religious folks do. I have told the JW's and Mormons that knock on my door that I don't believe what they do and quietly shut the door.

As far as I know, no.