Learn English – name for letters that “cross the line” (hang low) when written in lowercase (g, j, p, q, y)

A homoglyph is a character identical or nearly identical in appearance to another, but which differs in the meaning it represents.

Wikipedia has a detailed article on homoglyphs as well as one on IDN homograph attacks where phishers take advantage of this property to mislead their victims.

As for your spell-corrector, you should be able to class such occurrences under something along the lines of homoglyph errors or homoglyph conflicts. However, it's a technical term which might possibly be a little too esoteric for your audience.

This image appears to be an autologlyph as illustrated at segerman.org.

This form of expression is discussed in out sister site, Graphic Design, here.

The technique has also been called visual onomatopoeia as illustrated in Scientific American

Lauren Ipsum has suggested a neologism, fontomatopoeia.