I do think, purely from an i18n point of view that with settings like this it would make more sense to have this
$txt['mail_limit'] = "Maximum emails to send per minute (0 for no limit)"
Than combine two [...]
When translating such string, I tend to "improve" the strings in my language independently of whether the english string is changed according to my suggestions, to (attempt to) remove the problem (in this case, I'd maybe go with something like "Limit maximum number of emails to send per minute (Set to 0 to disable.)").
Especially, since the translators often do not see these two at the same time ...
In the case of two strings you at least
know which string is included, I find
string duplication to be a much bigger problem, because you have to keep the redundant copies synchronized (also as a translator, which means you need to keep a glossary), and sometimes don't even know which obscure other variable might be referenced or verbatim-quoted (and the original might have changed in the meantime). But yeah, variables are a problem, especially for non-technical translators (
also discussed here, more recently.
And yeah, every lookup of another variable (or search for a variable which name you don't know) takes additional time off of translation.
