The PHB describes a short rest as:

A short rest is a period of downtime, at least 1 hour long, during which a character does nothing more strenuous than eating, drinking, reading, and tending to wounds.

Here's the scenario.

The party holes up and declares the intention to take a short rest. The wizard casts comprehend languages as a ritual, and then spends the hour of the spell reading pages from a written text written in a lost language, one page a minute. While the literal words of the text are easy to decipher, due to the spell, it is challenging to make sense of the text as a whole, and the wizard needs to go back and forth to make sense of it, sometimes having to reread pages in light of the information on other pages.

Is this activity more strenuous than "eating, drinking, reading, and tending to wounds"? I am inclined to rule that it is, but I want to know if there are aspects that I am missing.

I am looking at the hour of the spell's effect as occurring during the short rest, excluding the time required to cast the spell, so the effort required to actually cast the spell is out-of-scope for this question. I'm just asking if the effort described to actually make use of the spell's effect is more than allowable in a short rest.

I'm interested in both RAW and in people's actual experiences with similar situations.

Thanks

It is not strenuous enough to stop a short rest

For the duration, you understand the literal meaning of any spoken
language that you hear. You also understand any written language that
you see, but you must be touching the surface on which the words are
written. It takes about 1 minute to read one page of text. This spell
doesn’t decode secret messages in a text or a glyph, such as an arcane
sigil, that isn’t part of a written language.

And, as you said, a short rest is:

A short rest is a period of downtime, at least 1 hour long, during
which a character does nothing more strenuous than eating, drinking,
reading, and tending to wounds.

Comprehend languages is is not a concentration spell, so it does not take any effort to maintain the spell. It allows you to retain the benefits, without any effort whatsoever. It is essentially allowing you to read completely naturally, like your own language, so long as you are touching the text. Therefore, it is not more strenuous than reading a book of your own language, which is within the parameters of the spell. Even if it was concentration, you could.

So, I would say you could easily action / ritual cast the spell before the short rest, and you would be able to enjoy that book during your short rest.

Reading with comprehend languages is probably no more strenuous than reading normally

The text of comprehend languages says:

For the duration, you understand the literal meaning of any spoken language that you hear. You also understand any written language that you see, but you must be touching the surface on which the words are written. It takes about 1 minute to read one page of text.

It doesn't say you need to concentrate, use your action, or do anything at all in order to understand spoken words, and the only requirement for understanding written words is touching the surface they're written on, which is already part of normal reading. It just says that you understand the literal meaning. In fact, understanding spoken language isn't even optional: the caster understands all speech that they can hear whether they want to or not until the spell ends. There is nothing in the spell text to indicate that reading or listening using the spell is any more strenuous than doing so without the spell. (One minute to read a full page of text is pretty consistent with how long it takes me normally to read and fully comprehend (i.e. not just skim) a page of text in real life.) Hence, I see no reason you could not benefit from a short rest while reading using comprehend languages. You probably would not say that hearing and understanding someone's speech using the spell should interrupt your short rest. So why should reading be any different than comprehending speech?

It's entirely possible that certain kinds of reading, such as focused study involving constant cross-referencing between multiple books and keeping track of many trains of thought at once, would be too strenuous to be part of a short rest. But that has nothing to do with comprehend languages.

No rulings either way, but I'd say no.

There's nothing in the books or SageAdvice or Jeremy Crawford's semi-official tweets. Me personally, as a GM, I'd probably say no, the wizard is too focused on his books to take the time to rest and benefit from a short rest. His mind is active and he's already focused on an activity, so he wouldn't be meditating on his spellbook to get his Arcane recovery for example.

You might be able to RP a medicine check from someone in the party to make sure the wizard gets food, water, and medical attention so he can regain hit die. I wouldn't consider tending to the wizard's needs to be too strenuous for a short rest for the helper.

I agree that with the other answers that the spell doesn’t make this activity too strenuous for a short rest. But given your description, I think it’s entirely reasonable to rule that working to understand what the text means - not just reading what it literally says - is a strenuous mental exercise, if the text is complex or obscure. This is something you could easily say about a wizard’s notebook, a history written very long ago with many gaps, a text created by a culture very alien to the reader etc - even if it was written in a language the character already knows.

The easiest way to model this is to have the character make an Intelligence check - perhaps using Arcana or History, if appropriate - to represent the cross referencing and note taking and so on required to work it out. You could also rule that the wizard can read the whole thing without making a roll, and give them a summary of what they learned which is subtle or complicated to understand or apply to their situation.

If it were me, I’d give them a choice - making the roll means they figure it all out to some degree, depending on the result (I don’t like flat-out failures on rolls to gain information), but they don’t get the normal benefits of a short rest; or they can just read it and try and figure out what it means afterwards, and they do get normal short rest benefits.