Actually, if one would read the subject of the thread it seems to imply eating alone with the teenaged daughter of someone else, but I dont think the poor writing skills confused anyone.
Unless the girl is 19 how many teenagers are in shidduchim? Is this thread about chassidim or communities where 16 and 17 year old girls are in shidduchim? why assume this is an issue of those in shidduchim. I guess I am guilty of assuming that the OP was addressing a scenario where a family has say a 15 yr old daughter and they invite a 17 yr old boy (or something similar).
Again, to those who stated that it is OK for a Rav or Rebbe to invite male guests with their teenaged daughters at the table and not OK for someone else to do the same, they simply failed to explain the difference, at least to me.