In most applications that I'm familiar with, a text cursor in insertion mode is universally represented as a vertical blinking bar:
As you can see, for some italic letters this creates visual artifacts: cursor overlaps part of the letter. This becomes particularly jarring when using a narrow and tall fonts such as Agency or Impact:
The problem is not only with the cursor, but also with the letter's background. For example selecting the letter "l" will make a large part of that letter hang outside the selection box, which makes it really unclear as to what is actually selected.
An obvious (and logical) solution would be to change the cursor from vertical bar to slanted bar, so that the cursor would have the same general slope as the surrounding letters. It could look something like this (only antialiased of course):
Similarly, for the selection (and general background rendering) we would replace the vertical rectangle with the parallelogram that follows the slope of the italic font.
Minor technical difficulties aside (how to determine the slope of the italic?) — what is the reason why no text editor uses a slanted cursor / slanted background within the italic text? Does it or does it not provide a better UX? If I were to implement this feature in my own text editor would the users find it useful or confusing?
EDIT: MS Word uses slanted cursor within italic text, however they fail to properly match the slope of the font under the cursor, and the cursor goes back to upright when switching to rtl script. Also, the letter's background is always upright. It looks like this:
(in case you were wondering: initial
Hel is highlighted here)