There is no other way, downloading a plugin specifically for this is not the point, and it is also the only thing I changed in the core file. WordPress should handle this in such a way that you can set or change it in WordPress itself without having to go straight into the core file.
I finally found it after a long, long, intensive search. It was actually very easy to find when you look at it that way, but with all the files it was very difficult to find where to start looking. I found it at
/ wp-includes / blocks / latest-comments.php on line 102
^^. Hopefully I was able to help someone who is also looking for it or wants to edit it without having to download / install an extra plugin ;).
