I thought both would be all caps but it seems that the language uses an initialism rather than an acronym. All my life I’ve been rarely typing out all caps Tcl like I’m one of the folk who use all caps MAC for the line of Apple computers.
TCL Technology Group Corp. (originally an abbreviation for Telephone Communication Limited) is a Chinese partially state-owned electronics company headquartered in Huizhou, Guangdong province.
Tcl (pronounced "tickle" or as an initialism[8]; originally Tool Command Language) is a high-level, general-purpose, interpreted, dynamic programming language.
It's an auto-formatting thing that HN does to submitted titles. If you catch it soon enough you can edit the title and it will be allowed as you specify, at least that was true the last time I tried.
Yes, that continues to work: (1) submit your post, (2) it's modified by HN based on rules such as multiple uppercases on a word, (3) edit the post title.