Please give SmartGit 19.1 preview a try and invoke Help | Check for Latest Build to get #14054 which implements this feature.

Will be fixed in 14051+.

When selecting the commit, you can click the name in the Details view to open the email client (or right-click to copy the email address).

Please check out the low-level properties log.graph.author.maxLength and log.graph.author.truncateLength.

The .tar.gz bundle already lets nearly every user run in on nearly every Linux.

You may try adding the line
smartgit.ssh.impl=sshj
to smartgit.properties.

Do you know that you can create own theme files?

Do you know that you already can use Ctrl+Space to write file names?

I wouldn't got that far with ahead/behind jigsaw pieces. Just the information whether a tag exists locally and remotely as well as equal/different would be enough for the majority of the use cases.