Can't firure out how to make a paragraph not indent

What you're seeing is not indentation but spaces getting inserted between your spans. Since we allow text content in a paragraph outside of a span on import - for example this:

<flow:p>some text</flow:p>

gets normalized to this:

<p><span>some text</span></p>

We're looking at the text in between your spans and adding more spans than you intend (collapsing the whitespace as we go, since that's the default behavior)

so this:

<flow:p>

   <flow:span fontsize="14">some text</span>

</flow:p>

gets normalized to this (and the span with the space at the beginning of the line looks like an indent):

<p><span> </span><span fontsize="14">some text</span><span> </span><flow:p>

What you'll need to do is eliminate the spaces between spans in your markup:

<flow:p fontSize='14' textIndent='0' paragraphIndent='0' paddingTop='4'><flow:span fontSize='15' >Juan Atkins<br/></flow:span><flow:span fontSize='12'>Pioneer Detroit Techno<br/></flow:span><flow:span fontSize='10'>Detroit, Mi<br/><br/></flow:span>A major electronic music pioneer from Detroit, ...only as imports.<br/></flow:p>