Lal has said in many posts that one does not stop all dosa akusala until one is an Arahant. Remember vaci sankhara is not only speech outloud, but conscious talking in the mind. Until manosankhara stops, it’s very challenging not to talk frivolously (talk w/o content or meaning) in the head.
What helps is analyzing the potential speech (outloud or in the mind) of how you may be hurting another or yourself. Frivolous talk sets the example that’s it’s acceptable and leads to bigger immoral acts (ie, gossip, slander, etc). What you don’t know about another person is what causes them to suffer.
Many like to talk about the weather, how bad it’s going to be. Some people have fears about severe weather and do all kinds of strange preparations for the possibility and suffer from mental agitation. So, weather which seems so mundane to one causes another to suffer and that’s immoral.
If what you have to say has meaning and useful (content to get a job done), then that’s not immoral as lay person. As a bhikkhu(ni), most talk that is relevant to one’s job is Dhamma, the most meaningful talk possible.
Donna