A family of Microsoft spreadsheet software with tools for analyzing, charting, and communicating data.
The built-in keyboard shortcuts in Excel 2016/2019 cannot be removed. Only shortcuts assigned by the user can be removed by the user.
However, most of them can be reassigned. The reason Alex Wang failed is that he assigned Command+I to the wrong command... Insert Row Above [as well as Insert Row Below] operates only in an Excel Table, not for an unstructured sheet.
If you assign Command+I to Insert Sheet Rows you should find that it works just fine to insert 1 (or more) rows above the selected row(s). If you wish, you also can reassign Control+I to the same command. Otherwise it will continue to invoke Italic formatting.
FYI: If you ever remove the user-assigned shortcut that previously was built-in the original built-in assignment will be restored automatically.