Excel macro is not respecting additional lines of text from within a cell. For example, if you have a list of things in 1 cell with each list item starting on a new line, but within the same cell, confluence is rendering the cell without respecting that new line. I have tested this locally on 4.2.8 with 2.0.14 office connector plugin. Tested against .xls/.xslx. A simple file with 4 cells did display correctly, however, a more complex document shows the text in the cell as described.
Support case reference for sample files which you can use to observe both behaviors.