Paul

You may choose a colourful style for the custom coupon message, or wrap the message in your own CSS class container.
It’s also possible to hide the default message from Woocommerce so that only your custom coupon message is displayed. 
(the plugin uses inline CSS to hide the default Woocommerce message).
Take a look at the screenshots for the coupon edit screen with the plugin enabled and some examples.
The meta box was implemented using the technique described on this blog post: 
http://wp.smashingmagazine.com/2011/10/04/create-custom-post-meta-boxes-wordpress/
The message styles were generated using this tool: 
http://www.bestcssbuttongenerator.com/

Woocommerce Custom Coupon Message

This plugin adds a meta box to the coupon edit screen where you can make your own customized coupon message.

pimwick

PW WooCommerce Copy Coupon adds a Copy link to the default WooCommerce Coupon pages. This makes it possible to duplicate an existing coupon.
<blockquote>
Check out <a href="https://www.pimwick.com/pw-woocommerce-coupons-plus/" rel="nofollow ugc">PW WooCommerce Coupons Plus</a> for even more features:
<ul>
<li>Clip Coupons – Be like Amazon! Require the customer to “clip” the coupon to activate the sale price.</li>
<li>Coupon Bulk Editor – Quickly change multiple coupons.</li>
<li>No Coupons Allowed – Mark a product so that it will never be discounted by a coupon.</li>
<li>And more!</li>
</ul>
</blockquote>

PW WooCommerce Copy Coupon

Does what it says!

You saved me about 10 clicks and 1 minute each for 90 coupons I had to setup. That is worth a 5 star review.

Did what it says it does.
Works out of the box.

Once installed, on the list of all coupons, you'll see a third option when you hover a single coupon, besides Edit and Trash there will be a Copy action.
Once copied, the new coupon will be opened so you can immediately edit the title of the coupon.

I'm a developer and have inspected the code which is neatly organized and I didn't encounter any errors/issues while running the plugin.

Excellent and simple

Simply adds a Copy button to WooCommerce coupons to make it easier to create new coupons!

Woocommerce Custom Coupon Message vs PW WooCommerce Copy Coupon