I don't have a copy of IE10 to test this with, but could you visit this page:
Once you are there, can you try dragging and dropping some text onto the 'drop content here' box and then post back the results (displayed below the box) into a reply here on this forum?
With that info, I can see if it would be possible for IE10 to support drag & drop of text.
Note it would be helpful to know what 'types' are displayed during the drag AND at the point where you do the drop (in case they are different) and if the content looks as you would expect. It would also be helpful if you could try dragging from a range of sources (e.g. Firefox => IE10, Word => IE10, Chrome => IE10, Notepad => IE10).