They’re trying to be edgy and use the obsolete thorn character (þ) everywhere you would normally pronounce “th”.
While I usually enjoy rifling through the UTF-8 character set for better/more-appropriate glyphs such as curly quotes instead of straight quotes and the numero glyph instead of the hash/pound symbol, the thorn character ain’t going to be making a comeback.
Edit: fun fact, even the temperature symbols have their own fully-assembled glyphs — Fahrenheit ℉ and Celsius ℃ come fully assembled as a single character glyph that you can use without having to cobble together shit. One of my biggest annoyances is seeing the degree glyph (which a math glyph, and has NOTHING to do with temperature) mashed together with a letter in a wholly inappropriate Frankensteining.