WordPress.org

Will this affect other plugins that already append stuff to my comments?

It shouldn't. I've already made a revision to specifically prevent this after discovering it on my own site. Let me know if you still have issues.

Does this also add a signature to posts?

Not at this time, though the functionality is being considered. If you're interested in it, let me know.

Will you be internationalizing the plugin?

If there's enough interest in the plugin in general, then yes.