Please take a look to this document/page-27:
http://richstyle.org/downloads/lpi-101-ar-ch-3.pdf
Text indent still look in the left side, whilest it should appear in the right side in this RTL document.

https://richstyle.org

This must be due to the default rule for <li> elements in our HTML style sheet:

li::marker {
    padding-right: 8pt;
    text-align: right
}

Currently we don't support direction-neutral keywords, otherwise we could do something like "padding-after" and "text-align: after". Perhaps instead you could override this rule like this:

*[dir="rtl"] li::marker {
    padding-left: 8pt;
    text-align: left
}

Does this improve the layout of your document?

Unfortunately, no
An indent still appear on the left side!

https://richstyle.org

Okay now I'm getting confused, exactly which indent are we talking about? Could you perhaps paste a short sample of HTML that demonstrates the problem?