Really, though, it's about "intent"...
I agree. But not only intent (as in intent to screw someone), but also knowledge that it's a typo and selling it at a non-typo price (which may make people not even question the spelling)
I'm also not talking about obvious mis-spellings. Some words have weird spellings and ask 100 people and 70+ would spell it the other way - that kind of thing.
A rule on declaring wouldn't work for these reasons, many times the owner won't realise it's a typo. I'm sure we've all at some point got excited about a domain only to realise at the last minute it's a typo. (The vv looking like a w gets me every time!

)
Maybe it should become accepted practice that we all do point out typos on a thread but in a positive way ("Great typo, definitely caught my attention!

")
Maybe. But if it was a rule, then maybe more people would comment on typos.
You mention the 'too good to be true names, and then we realise the typo', I'm talking about the domains that seem reasonable for £500 (sometimes more) and then you see that it's a typo and you wouldn't pay £10 for it.
Those are the names that make me wonder about some level of intent or knowledge without disclosing.
...We all have access to dictionaries and common sense, and having a name like "Mortage.co.uk" listed with a price of £100 (just a made up example) is hardly trying to defraud anyone in my opinion.
I agree, but this example (also made up):
morgage £2500 BIN
Even if the name is worth £2500 as a typo, I still feel like the typo should be declared.
I know it's buyer beware too. If I did something like this then I should only have myself to blame... but it all just seems a bit dirty.
For the record I haven't seen a lot of this type of thing on Acorn and really do think that this is a great community of very trust-worthy people
(just every now and again I see something like this and don't always want to be the person that says in the seller's thread that it's a typo)