TextCritical.net

Some works include mdash and ndash entities. These are currently not converted by the front-end and are therefore ignored. This causes the commas to be placed directly next the words without a space.

<span class="placename" data-key="tgn,7012913">Danube</span>
,which after all is but a small fraction of this
continent,and, by the destruction of the Persian Empire,
they afterwards added to that the dominion of 
<span class="placename" data-key="tgn,1000004">Asia</span>

Here is the original XML:

<placeName key="tgn,7012913">Danube</placeName>,&mdash;which after all is but a small fraction of this
continent,&mdash;and, by the destruction of the Persian Empire,
they afterwards added to that the dominion of <placeName key="tgn,1000004">Asia</placeName>. 

The actual parsed content in the database does not include the dashes. Thus, this is getting lost in the import process:

<placeName key="tgn,7012913">Danube</placeName>,which after all is but a small fraction of this
continent,and, by the destruction of the Persian Empire,
they afterwards added to that the dominion of <placeName key="tgn,1000004">Asia</placeName>

Apparently, mdash and ndash are various lengths of dashes:

– is an en dash (–)
— is an em dash (—)

See http://stackoverflow.com/questions/16550678/is-it-necessary-to-use-mdash-and-ndash-in-xhtml-or-html5.