Italic weight is not as wide as Normal weight.

The same text in italic is shorter than with normal font weight. The below line is my example text. If that line is present two times, one in italic, the other without, the italic line is shorter by about 5 character-widths as visible here: https://imgur.com/a/OF2PJjV

abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890

As many people use monospaced fonts in programming roles, this means that two lines, one commented and the other not, do not line up and are arguably no longer monospaced since there are multiple space widths depending on italics, bold, etc.