I think the second link is a great read and I agree with most points. If Tk had been moved to GTK or QT (probably GTK due to licensing) early on, it could have maintained its role for making portable GUIs a bit clearer. Though, in my eyes, Tcl/Tk still is the easiest tool to use portable UIs. Especially with Tclkits, you can make single-file executables, which are very convenient to deplay, I have had great sucesses with that.

Today, Python has grabbed a lot of attention from Tcl - for "programming" it might be the more elegant language, but for "scripting" Tcl is hard to beat. But it is ironic that Python still ships Tkinter as the default GUI solution. If any language, Python should have standardized on GTK support, it had good support for GTK, but never standardized it.

The Tcl syntax is a bit rough, but is built on extremely simple rules. This has two benefits. First of all, it is - that was what it was designed for - a great language to control tools, that is, script complex programs. Thanks to the syntax, every function immediately becomes a command a user can type, no complex syntax for the input required. In that sense, like shell scripting, Tcl sacrifices a bit of syntax suger for the developer for a nice interactive input syntax. It is vastly nicer to program in compared to the shell languages :) The second benefit ist the ability to extend the language by the users - it doesn't even need a macro system for that like Lisp. Tcl is one of the few homoiconic languages.

Finally, while Tcl isn't as activelely maintained and especially extended as other "modern" languages are, this cuts in two directions. The implementation is extremely robust and many features are very efficient. Of course the basic execution speed of Tcl code is one of the slower scripting languages, but the libraries it uses are excellent. It had high performing event handling many years before Node.js made that populer.