Tuareg: required Emacs version

Tuareg started to use elisp constructs only available in Emacs ≥ 24.3 (released in March 2013). Before we go further I’d like to know whether some of you need compatibility with older versions of Emacs. So far, I have not received any complaint, Emacs 24.5 is in Debian stable, and Emacs 26.1 was released in May, but maybe it is a problem for some of you. If so, please speak up explaining your situation.
Have a nice day,

Could somebody explain why tuareg introduces its own syntax highlighting instead of reusing the standard one (aka font-lock-keyword-face and friends)? It’s annoying that it blatantly ignores my colorscheme.

This is off-topic but the reason is that there are concepts in OCaml that do not directly map to the standard faces. For example, Tuareg uses the standard font-lock-variable-name-face for variables, font-lock-keyword-face for do, with, whenfont-lock-preprocessor-face for cppo preprocessing, but tuareg-font-lock-governing-face for let, module,… and tuareg-font-lock-module-face for module names (the latter being inherited from font-lock-type-face so it should follow your color scheme).

In answer to your original question, I think not supporting versions older than five years is perfectly reasonable, especially when we’re talking about open source software that anyone can upgrade without significant cost.