Thanks @squareclouds-design
@ezchile solution sounds good 
There has been some discussion on this a little while ago:
Basically we were hoping Redactor would release a fix.
Redactor 3.1.8 is running in the latest version of Pulse and 3.2.0 will be out in 5.3.4 - but doesn't look like it addresses the issue:
For now the best work around would be:
- pasting in HTML mode
- using the CSS solution provided by @ezchile