I'm not sure that I find these supposed counter examples particularly convincing.
Arguments based on the names of games are surely a red herring.
The games themselves may well be uncountable, but that does not of necessity confer "uncountability" (or otherwise) upon the components of their names.
Nor do those components always turn up as invariant singulars, eg. a game of 'snakes and ladders' ('chutes and ladders'); 'cowboys and Indians'; 'cops and robbers'; 'draughts' ('checkers'); 'fox and geese'.
What's the game we play here? Let's call it Q&A. Are its subcomponents plural or singular? For me it could be either so long as I presume that the 'Q' and the 'A' stand for what we might expect them to, because both 'question' and 'answer' are countable.
However, if the 'A' stood instead for 'advice', a properly uncountable noun, it would be a very different story.
I think that the same is true of the 'game of sale and refund'. It could easily have been 'a game of sales and refunds' without jarring anyone.
Similarly "'
(There will be) No refund for purchases below £10'. The plural form also works here: '(There will be) No refunds for purchases below £10.'."
The fact that the plural also works here demonstrates that 'refund' is countable. You could not do that with, say, 'information'.
I think a rule of thumb is 'can I sensibly put "a bit of" in front of it?'. If the answer is yes, then it can be uncountable. If the answer is no, then it's always countable.
I'd like a bit of peace

I'd like a bit of information

I'd like a bit of advice

I'd like a bit of compensation
I'd like a bit of refund??? I might say this as a joke, but I don't think that I would ever wish to write it. Others may feel differently.