I've never ever felt ashamed of having PND -- though before I was diagnosed, I knew next to nothing about it; I just thought it meant feeling suicidal (which I never did, thankfully). I never dreamed it could happen to me. I did post under another name on MN when I was struggling with it, but that was because I didn't feel like myself. It wasn't to do with being ashamed, just that I was conscious that this wasn't me, IYSWIM.
I was so relieved to find out that I actually had something wrong with me that I felt a weight lift when I got the diagnosis, and I certainly don't hide the fact (in RL or on MN) that I've had it, and that PND is hell. I'd love to think that I've educated people about it a bit. The trouble is, everyone's experience of PND seems to differ so much, it's really an umbrella term. I don't think you can expect everyone to really 'get' depression. I only got one or two dismissive comments in RL from my sister but I knew she just didn't have a clue and so it didn't bother me too much.
Actually I struggled much more with the idea that I'd need ADs. The thought of being on head meds for a length of time was the scary/shameful bit, for me. But I got over that.
I've never read a Feeling Depressed thread that has turned sour.
MN was so helpful to me when I was ill.