Mirror Modifier : leave uv seam or hard edge on axis edge

Hi

Mirror Modifier / low poly modeling

It’ll be great to decide what this modifier is doing with edges on the mirror axis in terms of uv seams or leaving sharp or soft edges there.

Often I'm left with collapsed uvs which is very annoying when for ex. you want to bake some data on it and have permanently overlapped uv islands (unwrap is treating it like one uv island // also uv pack master doesn’t recognize it as an overlapped uvs // select linked (seam/uvs) for further selecting only one half also doesn't work ).

Of course you can mark it by hand but it could be automated making life a lot easier.