Be honest-best policy.

Pay no attention to it. If you're wanting to approach them romantically, you'll chat first and you can ask about it. I wouldn't give it any concern. How many statuses on "dating" sites are a lie anyway?

Would you want to meet someone who was secretly married?.... Massive question marks hanging in the air... Will they split, will they not?

It's deception.

My policy is to steer clear of people who have undeclared romantic statuses. At least when it comes to dating.

I put 'I'd rather not say' because I was at the time still married to someone who broke my heart. I am with someone else in the broad sense of the word but not in a romantic going places sort of way.

it could mean you are divorced and just don't want to thnk or talk about it or you have been single all your life and feel embarrassed or want to talk about whatever it is at later date etcetc

Could be married but the marriage is in crisis, and about to end.

Maybe they're separated and haven't seen their spouse for a while.

When I was newly widowed, I checked "rather not say" as I was nervous being alone with small children and did not care to advertise such vulnerability on the internet.