I don't think there is any easy way to do this in SQL.
There is no easy way for a SQL query to know that the value in one record is a part of the value in another record.
If there truly are only two records in your result set it wouldn't be too hard, but what if there were 200 records?
And KuriosJon asked you what you wanted to get from
And you answered
That's even tougher, as now you are asking SQL to recognize that "two three" is two separate words, split up those words, and then group_concat them back to get the commas between them.
CAN this be done? Sure. Anything *CAN* be done. But it would be a messy Stored Procedure that would probably need to use a cursor.
I think you would be better off just getting "thing,real thing" via group_concat and then using PHP coding to consolidate that down to "thing,real".