As mentioned here, markdown do not support right aligned text or blocks. But the HTML result does it, via Cascading Style Sheets (CSS).
On my Jekyll Blog is use a syntax which works in markdown as well. To "terminate" a block use two spaces at the end or two times new line.
Of course you can also add a css-class with {: .right }
instead of {: style="text-align: right" }
.
Text to right
{: style="text-align: right" }
This text is on the right
Text as block
{: style="text-align: justify" }
This text is a block