Is that necessarily OCD? I do that sometimes, but I think it's just regular worries coupled with a poor memory (and inattentiveness), that leaves me often unsure if I really did something like lock the car door.
We all have kidneys that don't work perfectly, so we are all on a continuum of kidney failure, however you'd describe some people as having kidney failure and others not, only a few people would be 'borderline'.
I appreciate that may not have been what you meant, just that your argument lies close to that kind of logic (though maybe by saying non-linear you mean to avoid this trap).
I think it's incredibly useful to realize that all of us experience symptoms of anxiety and depression, intruding thoughts and compulsions, but those who with the problems are just those further along the line. It's not diminishing the issue, it's humanizing the sufferer. They aren't "crazy", they are suffering from something we all can relate to, but just in a manner that's unmanageable.
How differently should we treat "sick" people? Do they milk their diagnoses extra sympathy as alluded to by stephengillie elsethread? Honestly I don't care too much about that. A much bigger concern is that labeling people "sick" justifies the creation of a self-sustaining industry dedicated to their "treatment". Even if nearly all of the researchers and physicians are well-meaning (which I believe), we need to be skeptical.
Most of all I resist the othering of the "mentally ill". What we regard as "normal" entails quite a range of irrational and strange behavior. I personally believe the best model is that nobody's "normal", yet medical intervention is rarely justified and ostracism is never justified.
I think it's a bit of both really, a bit of OCD, a bit of anxiety.