In ArcGIS Pro 2 when editing the field map parameter in the Table to Table tool as soon as you make any change to the field name the alias instantly becomes the field name so loosing any additional characters you might have put in the Alias.
This is really annoying and makes editing the field map very tedious as I have to undo all the automated changes!
For example I have a field which is based upon a join to the table and the field name is tblRoutesLinkKonyaDistance and it's alias is "Linking to Konya Distance (Km)". Whilst setting up the field map to define the output table I want to change the field name to LinkKonyaDistance. As soon as I edit the field name the Alias reverts to the field name but I don't want that I want the Alias to remain as is.
I've yet to explore if this happens in of other tools that use field mapping but I suspect it does.