You've seen the descriptions, well here is what the traders really mean
'Untested' - Unrepairable, knackered, he's had a go and butchered it
'Damaged whilst changing the fascia / cover' - They've had a go and butchered it. If its a flip or slide phone then the ribbon is probably damaged, some can be changed with skill, others require advanced soldering skills and can only be accomplished by professionals.
'Purchased in a job lot' - He buys, sells and repairs phones, this is the rubbish he couldn't fix.
'Received as part of a trade in' - Same as above.
'It got wet' - Stay well clear, water damaged phones are a nightmare
'The phone says 'Inactive Sim' - Sony Ericsson phone that is barred / blocked / stolen / or someone defaulted on their contract.
'The phone says 'Sim Registration Failed' - Nokia phone that is barred / blocked / stolen / or someone defaulted on their contract.
'The phone has signal problems' - Again same problem as above but hidden meaning so eBay do not remove the listing.
'The phone says 'Limited Service' - Samsung phone that is barred / blocked / stolen / or someone defaulted on their contract. Alternatively, has hardware faults that require components changing, impossible for the amateur.
'Not tested fully' - Probably has more faults than described, just a 'get out' just in case
'Well used' - Scruffy as a gypo bathing in mud.
'Could do with a new case' - Same as above.
'Doesn't / won't charge' - Water damaged (see further above).
'Phone has unknown security code' - The code is known, he just put one on because the phone is barred/ blocked !!
'Don't have a charger to test' - Fair enough if its a strange make of phone, but if its a Nokia, Samsung, Motorola or SE phone, its definitely got more faults than San Andreas.
'No battery to test' - Same as above.
'Missing battery cover and battery' - The phone has been sent back to a manufacturer's warranty repair site and deemed beyond economical repair !!!
Don't get me wrong, sometimes you do stumble across an individual selling their old phone that can be repaired. But look at what these seller's are selling as well as what they are buying. If they're buying faulty phones then you can be sure that the faulty phones they are selling are beyond repair.
And another golden rule - ask questions, never ever ever assume things. Get as much information from the seller as he/she will divulge. If they won't tell you something or avoid the question - assume the worst.