I understand that concept, but does coins.ph only give out one address for many individual members to use?  If that is indeed the case, then there's no merit to OP's suspicion. 

Even if it isn't true, sending coins to someone's address every week doesn't necessarily mean they're alt accounts.  There could be any number of reasons someone would do that, and to hand out negative/neutral trust based on that evidence alone would be unfair IMO.