Yobit seems working for me just ok, but still signatum on more exchanges would be great. Those scam accusation are somewhat worrying me.
If you have a look through the post history of those making the accusations, you will not be worried.
They are perpetual FUDers, with little, to zero credibility on Bitcoin Talk.

says the guy with -8 trust
this coin is scam you have been warned, only a handful of members are holding a big bag of SIGT's waiting to dump for a "good" price
Volume on yobit is fake and fully controlled by those handful of members
If you are searching for credibility just look up their accounts: all new ones registred 1 month ago
say no more
Hard facts have been posted this coin is a exact copy of blackcoin
but why? because 4% of all btc wallets hold 96% of all btc...what we doing now? ok lets say to everyone that btc its a scam and the 4% wait to dumb the coins to the people ok?