When importing paragraphs with negative text-indent from HTML, e.g. 
<p style="text-indent:-12px;">
test
</p>

they should be imported with HangingIndent + the same value with negative sign for LeftIndent, e.g. HandingIndent: 12 AND LeftIndent: -12.

Also, margin-left should be combined with the text-indent, e.g.
<p style="margin-left: 16px;text-indent: -16px;">
test
</p>
should be imported as HandingIndent: 16 AND LeftIndent: 0.