The main issue is the fact Excellon files have no coordinate fine format definition.
Only the units are defined.
Units are floating point numbers or integer numbers.
Integer numbers can be defined as 3.3 or 2.4 numbers (mm/inches)
However some files (altium drill files for instance) use an other notation.
This fix is a workaround to accept 2.x (inch) or 3.x (mm) notations.
Fixes: lp:1754121
https://bugs.launchpad.net/kicad/+bug/1754121
Fixes: lp:1782053
https://bugs.launchpad.net/kicad/+bug/1782053
A structured comment is a comment line starting by "G04 #@! " and in fact containing
a X2 attribute. It is used to create Gerber files contianing X2 metadata, but compatible
with X1 file format
jean-pierre charras