The above reasons against the trading forum hold true, but there is one ultimate reason why it'll never happen on these forums, and the Spyderco crew will not want to say it.
Simple: promoting the second hand market is against their business interests. If they put it here on their own site, a curious customer will think "Ooh, I can get a LNIB Para 2 for $90 instead of $100". One para 2 can change hands 10 times on the secondary, Spyderco and its dealers pocket money only once.
An extreme example is the video game industry- because of the nature of video games as physical media, gamestop sells the a game, buys it back for pennies on the dollar, and repeats. The developers recieve money only once.
Gamestop has singlehandedly killed off many struggling game studios in the fast few years.
Note that this is an extreme example, but it still applies.
Now, secondary market arguably has it's benefits (I would personally disagree),
but it is definitely not in the interest of a first party to promote it.
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