teaching - Is there a standard of professionalism in academia requiring me to hide self-harm scars if I'm otherwise comfortable leaving them exposed?

I'm a student intending to stay in academia, and I'm reaching the stage where I've begun to TA classes. If all goes well I'll be teaching courses for the rest of my career, so I want to make sure I'm doing it right.

I have a series of scars across my arm that anyone with experience or awareness of the issue will immediately realize were self-inflicted. I have not added to them in enough months that they are old and a little faded, but they are still very visible. Personally, I've grown comfortable with leaving them exposed – a stare from a stranger now and again won't hurt me.

But in a classroom environment I'm uncertain – is it possible that the emotional vulnerability implied by the scars would compromise my relationship with my students as a teacher, that they might lose respect or trust in my competence? Should I perhaps cover them because they may bother students who have been affected by the issue?

I understand that a great deal of this is based on the individual: whether they're comfortable, the way they wish to present themselves to their students, how private they wish to be, and so forth. Setting this aside, is there simply a standard of appropriateness with respect to how much I should implicitly reveal? Obviously it would not be appropriate to launch into a ramble of my mental health history while holding office hours, but would the existence of the long story implied by my scars be something I should take measures to keep from my students? And are there guidelines that would generally apply to people in similar situations (for example, if a recovering addict had obvious needle marks)?

I should add that I'm a Canadian studying in the United States and that I have seen one instance of a graduate student in the same situation as I am – she did not choose to cover her scars.