Sorry I've been away so long.
I agree it's really hard to broach the subject.
Hubbie and I have talked about it (started really with the support from a worker) and he wants to be supportive but really can't get his head around how anyone can want to self injure.
He said "If she wants to hurt herself it's up to her"
I'm not sure that was too helpful, but better than a kick in the teeth. He has tried helping by being someone I could be accountable to, but that didn't work at all, so I don't discuss it any more. My fault, not his.

I feel for your situation. There's the elephant in the room everyone is avoiding mentioning, either to avoid hurting the other...saying the wrong thing...being rejected....take your pick!

I'm not sure if this was any help, SI is tricky which ever way we look at it.
The important thing for me is if they care for our welfare I guess.

The first time I started to talk to him about SI I just talked about reasons and benefits "some people" feel.
Then later pointed out why I "might" do it myself.

I can't remember how it went from there, but he has at different times expressed sadness at injuries, or more recently referred to "the evidence"

I guess it's a bit hard not to notice scars and dressings however unobservant he is (which is very unobservant).
I'm lucky he's not a shouty person, but he was scared of hurting me if he raised the subject.

Best of luck if you decide to raise the subject. If you don't, I guess if you love each other you'll find a way to work around it.

I'm rambling now, so I'll just send warm hugs