If a seller (who is also a buyer) orders from you without messaging you first, if you then send them a message in the Fiverr inbox, any message will affect their response rate and time when it shouldn’t really (at least not unless it’s relating to one of their gigs that they’re selling). There could also be a big timezone difference between the buying seller and the seller.
Any message sent to a buyer (who is also a seller) who has recently made an order with you will more likely be about the order they’ve made with you (maybe updated info about the delivery or maybe they left a tip or something) and the seller who purchased may also be in out of office mode (so that would be another reason for a message to them that is not about their gig shouldn’t affect their response rate but would).
What do you think? Shouldn’t such messages not affect the buying seller’s response rate/time? What if about if you wanted to message them after the order is complete (but without spamming) but don’t want to affect their response rate/time (especially if they’re “out of office”)?