Microsoft@Mike Glenn - Which version are you seeing this issue? Do you have a screenshot somewhere showing the problem and what you'd like it to look like? Sorry, I'm not familiar with the problem so just want to make sure I fully understand. Thanks!
@Brian Jones : Thanks for your interest in investigating this issue. To provide an example, I had to first recall that I was working in spreadsheets created by someone else in which they had selected thicker borders around all cells. To assist with QA, we had to compare rows of data with paper forms—thus requiring us to quickly glance back and forth between cells in the spreadsheet and the associated section in each form (handwritten of course to make it even more challenging). I've attached some sample data with thicker cell borders to demonstrate the difficulty of visually spotting the highlighted cell. You can imagine the additional eye strain caused by frequently shifting one's gaze over and up to the row and column indicators if you can't immediately find the highlighted cell. Difficulty is further increased on dimmer, lower dpi displays. This is an issue in all versions of Excel that I'm aware of.
Temporarily removing the thicker cell borders is one workaround to make the selected cell stand out more. Nevertheless, additional highlighting options for the active cell would be significantly better—especially for individuals with less-than-perfect vision. This could be seen as an accessibility enhancement.
Expand the image fully for the most realistic view of the active cell contrast problem:
