Wait, so HN normally filters the more odd Unicode characters, but does not filter codes from the Private Use Area?
Note: Since this is the Private Use area, the character you used does not display the same on every device. In my browswer, it displays as a box containing “F8FF”; if I copy it to a nearby terminal window, it shows up as “(t)”. According to the ConScript (unofficial) Unicode Registry for private use characters¹, the character you used is the “KLINGON MUMMIFICATION GLYPH”. I assume that you meant to display some sort of Apple logo?