In the feedback section of an assignment submission, the feedback comments are displayed in a summary box which can be expanded to display the full feedback text. 

In Internet explorer 11 the expand and contract icons cannot be selected. 
The cursor does not change to a 'pointer' when hovering over them either.

Possibly the same issue as MDL-67442

The issue can be resolved with the attached patch, which replaces use of

display: inline

with 

display: inline-block

 for the affected <a> tags.