Should you use a comma/period after "Thanks"/"Regards" in email signatures?
If you consider it to be a phrase that simply spans two lines, I'd say:
Thanks,
John Doe
is correct. Without the comma it would imply that you're thanking John Doe. It's certainly the one I use personally, not that that's a particularly good back-up for this answer. I can't say I've ever seen anyone use it with a ".", that just looks wrong to me.
The
Thanks.
form tends to seem vaguely abrupt, clipped, perfunctory, and rude to me.