If you're familiar with reading raw HTML in a plain text editor it may be worth looking at what Word produced for your bullet list in the filtered HTML file.
A clean bulleted list would look something like:
Code:
<ul type=disc>
<li class=MsoNormal>Item 1 with bullet. Make it long to see the effect of wrapping to the next line.</li>
<li class=MsoNormal>Item 2</li>
<li class=MsoNormal>Item 3</li>
</ul>
If you've done a lot of formatting, Word is capable of making a real mess of lists, tables...etc...
the list is long.
Also, I believe MOBI format is very limited with what it can do with margins. Have you tried converting your HTML to EPUB and viewing in the Calibre Viewer. If the problem, also exists there it would suggest a problem with the source HTML. If not it may be the limitations of MOBI.
I'm not a Kindle user, but perhaps someone will stop by with more relevant info.
Edit: I've just had another thought. If you have full justification specified that may make minor adjustments to spacing in order to achieve the straight right margin.