The Currency Exchange board is meant for selling and buying BTC for fiat currency. If within your Currency Exchange thread you offer to sell or buy alts for BTC / fiat / other alts in addition to offering to buy and / or sell BTC for fiat, that's allowed 1. However, if you're only offering to buy / and or sell alts for BTC / fiat / other alts, that thread belongs in Marketplace (Altcoins).
1 If a user is trying to circumvent the restrictions by mostly making a thread about exchanging alts while only adding a token mention of trades between BTC and fiat, a moderator may opt to move the thread to Marketplace (Altcoins).
Well, that does make a little more sense, but is a few continents away from pinned thread... or at least to the interpretation of it.
I don't know if a revision of the current definition of the board would make sense, it sure would help some serious trades happen, but maybe the spam generated by the change would be just too much
Thanks for taking the time to explain it tho