Take for example Matthew 9:10-13:
While Jesus was having dinner at Matthew's house, many tax collectors and "sinners" came and ate with him and his disciples.
When the Pharisees saw this, they asked his disciples, "Why does your teacher eat with tax collectors and 'sinners'?"
On hearing this, Jesus said, "It is not the healthy who need a doctor, but the sick. But go and learn what this means: 'I desire mercy, not sacrifice.' For I have not come to call the righteous, but sinners."
My younger self thought of them as similar to sarcasm quotes, to be read while smugly preening over the blindness of the Pharisees. That seems entirely inappropriate for a Bible translation, though, and the only explanation I can come up with for them being there in the first place is to imply that the Pharisees did not consider themselves sinful, or to imply that Christ's dinner guests were not really sinful after all. And then that old saw that goes "well, we're all sinners" comes tramping into mind...
I notice that the NIV 2011 took them out, but have the translators (or anyone else) ever explained why they were there in the first place?