Could you please describe in more details what exactly you mean? Note, that branches and tags in Git are just named pointers to commits. They are not part of commits.

No, Copy Message works for multiple selected commits - at least in the latest SmartGit 17.

Why not use Copy Message?

Will be harder than usual because of the index saving which is special in the Index Editor.

What about a hook that rejects screwed up line endings?

What if a multiple branches or tags point to the selected commit?

SmartGit supports different SSH keys for different servers. For multiple ~/.gitconfig files, please vote for http://smartgit.userecho.com/topics/350-full-multi-profile-system/.

Quite often it happens that when I'm on develop starting something that it gets larger than initially expected. Then creating a new feature works perfectly, so I reckon it seems to depend on what branch you actually are starting to work.

You already can do that. Just select both files and invoke Query | Show Changes. You will be asked whether to "Compare with Each Other" or "Compare with Repository".