Late to the party, but I now take a narrow view of what Latex questions should be allowed, and since dmckee's answer is the currently-accepted and highest-rated one, and since it's particularly terrible, I'll make my case by rebutting him.
TeX and all its derived languages are Turing complete. Every document is a program, and problems are equivalent to "How do I get output X?" questions in any other language.
This reasoning disingenuously overstates the sophistication of the typical Latex question on S.O. The fact that you can treat Tex like a Turing machine is, for a vast majority of questions on S.O. (and elsewhere), nothing more than a nice bit of trivia that factors rarely into the solution.
Now, if someone does need the programmatic power of Tex, such as if they're getting bugs while writing an original package, then that's a programming question, because they're actually programming. But it's fallacious to say that because a handful of Latex questions involve T.C.-ness and are programming-related, then any Latex question would involve T.C.-ness and be programming related.
Many problems are solved by "redefine macro \foo" or "define macro \Foo that extends \foo". These are programming solutions to programming problems.
Simple transformation macros could go either way, probably more in favor than against. Even so, it's the same sort of fallacy you committed in your previous point to think that this extends to any arbitrary question.
Some problems are solved by "get package Bar from CTAN", but if these are out than so are perl questions where the answer is "get Bar from CPAN", or even C++ questions where the answer is use Boost::Bar.
First, "some problems?" Try "most." But that's debatable unless someone wants to perform a census. But, that's not what's the best part. You see, Perl questions where the answer is "get Bar from CPAN" are justified because it's established that Perl is a programming language. C++ questions where the answer is "use Boost::Bar" are justified because it's established that C++ is a programming language.
You're arguing, then, that Latex questions where the answer is "use this Latex package" are justified because it's established that... wait, what was that you were trying to prove, again?
If "it's a layout language" is an acceptable argument against LaTeX, it applies even more to HTML and CSS, both of which are widely accepted and much more prevalent on StackOverflow.
I agree with your statement that Latex questions are comparable to another class of questions that are a clumsy fit for S.O.? Or were you doing the whole "two wrongs make a right"-style of justification. In any case, perhaps I should point out a certain site called Doctype.com, which is meant for HTML and CSS Q&A? Mayhap you've noticed the link to the site in the page footer on every Trilogy site? Mayhap you saw the same getting advertised on the Official Stack Overflow Blog?
While we certainly encourage web design questions involving HTML and CSS on Stack Overflow, it’s intended first and foremost for programmers. So if you’re a web designer, and less of a programmer, you might find a better audience for your question (plus some cool auto-screenshot capabilities) at Doctype.
What does this mean in practical terms?
- Our /faq will direct designers with pure HTML/CSS web design questions to Doctype, to better serve this subset of our audience.
- Our “hero roster” at the bottom of every page will offically list doctype.com as a member of the team.
- We will host Doctype discussion on meta, so the Doctype developers can participate and respond to community reactions and feedback for their site.
Moreover, I do not see any hypocrisy in stating that "O.K. guys, from this point on, if you're not making Tetris in Latex, your question's getting locked," and simply grandfathering in all the existing Latex questions. I do have a problem with using inertia as a reason to maintain the status quo.
Also, with the passage of time it now seems fairly likely that Latex and co. will get their own dedicated S.E. site, which weakens the argument that Latex is allowed on S.O. even further.