Like Petr mentions, currently the plan is to make a separate Merge command which on curves will fuse 2 curves into one smooth segment instead of what Join does, and then have it also work on edges to fuse edges together.

Do you guys think it would be better if Join on edges did this merging operation instead of what it currently does?

Sometimes the current behavior can be useful, for example making a sweep rail from a bunch of edges you can just select them and use Join currently to make that happen in one step, so that's one reason why I'm thinking it should be separate.

- Michael