When you reply to a post in Yammer using email, you can remove your email signature from the post. This is particularly important when your email signature includes attached graphics and logos. Each graphic will be attached to the Yammer post - not pretty. A common #YammerTip is to place two hyphens on a new line.
This will prevent Yammer from posting any text below the two hyphens. It's a good idea to include the hyphens in your email auto signature.
But what if you want your signature to look good, without displaying two -- hyphens?
Easily solved! When you create your auto signature, make the hyphens the same colour as your email background - in most cases, white.
The auto signature with "invisible hyphens" will prevent your signature from being added to the Yammer post.
With the increase of organizations using Yammer, it would be a good move for email signature management systems to add a simple check box option - "Using Yammer?" This option could add the "invisible hyphens" for you.