Diff on those two files shows that all the line has changed. Does not get granular to the character.

[deragon]

Using the code of icdiff from this repository, branch master, as of 2021-02-18, the following occurs:

As you notice, the whole line is shown as changed while actually, only some characters have. Here is what vimdiff shows:

Same output with meld. Thus everything suggest that the problem is with icdiff and not the files.

Command used (click on the files below to download them):

icdiff filea.txt fileb.txt

[jeffkaufman]

icdiff is a wrapper around python's difflib. You could report this to python if you wanted, but unfortunately this isn't the kind of thing icdiff can fix.