The main issue here is that there is no support in Excel for numbered or bullet list. In fact, the only thing that Excel supports inside a cell is to change the font, so that's what FlexCel supports.
You can get list of currently supported tags here:
But that would be a hard-coded conversion: That is we wouldn't end up with a list in Excel, but just plain text. If you added another item in between the Excel text, the numbers wouldn't change.
In any case, let me see if it would be feasible to do such a conversion: If possible we can add it. My main fear here is that it won't probably work as most people would expect, because Excel lacks and support for lists inside its rich text format.
Just to let you know we implemented it. As said, it is not a perfect solution because Excel doesn't have bullets, so we manually emulate them by entering bullet characters.
But I think the result is acceptable, and in fact seems to be better than what Excel itself imports.
There are some differences because there is some badformed html on purpose for testing (missing closing tags, etc), but all in all I think it is ok. The main issue is that if the text is too long it will wrap to the start of the cell, not keeping the indent. I don't think it is possible to keep the wrapping indented in Excel.