OP I haven't read the full thread but wanted to tell you this happened to me and YADNBU!
My lifelong friend has always been aunt to my dc, right after my dd died my friend's sil named her next baby the same name. So now forever my friend is stuck with two nieces with the same name, 1 dead and 1 born right after.
Everyone thought it was fucking weird. No explanation has ever been volunteered apart from maybe she liked the name.
I cannot tell you how fucking angry and uncomfortable this has made all information or conversation regarding new child and to be completely frank I will be happy to never see friend's sil again. I think she is a fucking ghoul.
It is a stab in the guts every time I hear new child spoken about in the place of my child and always will be. I feel sorry for the child who will always have that shadow in the background too, imagine growing up and finding that out later on?
If she had asked I would have said middle name only please if you must but the first I knew was a birth announcement card.
Even if something like that was done in a post birth drug haze you would expect any right minded person to change it, switch to middle name or use a nickname henceforth to avoid upset once it was pointed out.
One of my dc has a middle name after a a person close to me who died a very long time ago, I asked the family first for permission, they gave it their blessing and I would have not used it otherwise.
It takes permission from the living to honour the dead.