In Kate, the grey/vertical strip down the left hand side of a document that displays line-numbers needs some whitespace added b4 the line number. Once you get into 4-digits, the line #s are crammed against the window border with no space, and the 1st digit's actually cropped. A screenshot's at the URL above. Reproducible: Always
It's a known issue with the oxygen style. *** This bug has been marked as a duplicate of bug 312321 ***