<p dir="auto">Cmd + Shift + D should duplicate not only current line, but current selection if available.</p>
<p dir="auto">Sublime Text allows it !! <g-emoji class="g-emoji" alias="hushed" fallback-src="https://github.githubassets.com/images/icons/emoji/unicode/1f62f.png">😯</g-emoji></p>
<p dir="auto">I had a line over 80 characters, I added a newline and realigned the code.<br>
I then changed another parameter and the line (the one I originally added the newline to) is again over 80 characters. I added another newline but this time atom duplicated the line below it!</p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://camo.githubusercontent.com/c7f683e9e3299e815cc149419eb1c52af6299197904768b8f382e52ed3570e63/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f373439322f37363733392f38656435346234302d363066642d313165322d386564652d3863343435343938633630312e676966"><img src="https://camo.githubusercontent.com/c7f683e9e3299e815cc149419eb1c52af6299197904768b8f382e52ed3570e63/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f373439322f37363733392f38656435346234302d363066642d313165322d386564652d3863343435343938633630312e676966" alt="atom-line-dupe" data-animated-image="" data-canonical-src="https://f.cloud.github.com/assets/7492/76739/8ed54b40-60fd-11e2-8ede-8c445498c601.gif" style="max-width: 100%;"></a></p>