(a) I don't think we can agree in the end starting from this though. In general, scripting languages are extremely popular and just fine for most people, and editors with tons of quality extensions (Emacs, Vim, Sublime Text, VS Code) all have them written in those. Even if your argument was valid about building a large system, here we're talking editor extensions.
(b) If you're accustomed to compiled languages (e.g. seasoned C/C++ programmer), then sure you are not. But setting up the correct environment, debugging, etc is more difficult for C/C++ than for any scripting language, and a big barrier to entry.
(c) The necessity arises from wanting to get more extensions, and thus attract more coders. If you only allow C extensions, you'll get much less extensions (and not necessarily higher quality either). So you either give a scripting extension language (low barrier, easy access, lots can start using it), or many scripting langauges (even better), or you allow for many compiled languages though an API/ABI (higher barrier, but at least not limited to a single one).
I hardly believe this is a controversial point. Literally almost any app that ever wanted to get more extensions from users went that route. They didn't tell them: "just set up GCC, get the headers, and be on your way", because they knew the majority of potential users (extension authors) would be put off.
In fact, even hardcore C++ AAA game developers add a scripting engine, not for end users, but to make it easier and faster for themselves to develop the logic, behaviors, etc, of the game, exactly for the same reason: outside of the critical paths C++ is overkill, and slows down momentum.
(d) So, not exactly patently false, but only "patently false if you also make a special architecture choice for it" (off-process, messaging, etc).
> f) Claiming "memory leaks and such" is a bit too abstract for me to understand what you mean.
(f) A scripting GC makes it from less easy to impossible to have memory leaks in your extension that e.g. C.
I do not have any experience in AAA game studios. That said, I haven't heard of scripting languages being used extensively in recent years: A cursory glance at GDC presentations over the past 5 years doesn't reveal much emphasis on scripting languages or on the great successes you allude to. I gather from this that they've mostly been abandoned, excised from engines, or play a relatively insignificant role in the engines used for such games.
I'm not convinced that compiled languages constitute a significant barrier to entry merely because they are compiled and have low level facilities. That would only be possible if programmers somehow didn't have a working understanding of how CPUs and memory work, could only function with a garbage collector, and were unable/unwilling to run compilers like gcc or debuggers like visual studio, but such a person wouldn't meet the definition of "programmer" anyway, I don't think. My assumption is that a text editor, in particular, is being written for programmers.
>I gather from this that they've mostly been abandoned, excised from engines, or play a relatively insignificant role in the engines used for such games.
Nope. They've never went away.