It is not the normal default setting for an Edit Box formatted field. Both the Formatting tool bar and the appearance tab of the inspector have controls for selecting the alignment (justification) option for the currently selected field, but I have no likely idea why each newly added field would start with right justification nor why a duplicated field would default to this alignment.
Are your location settings on your computer for a part of the world where text is read from right to left? Could you have a font specified that is for a language that reads right to left? (not a likely scenario here, but if fits what you describe to some extent...)
Does the layout theme make a difference? (If you create a new layout, select a different them for it and then add a field to the layout, what default justification do you get?
If you create a brand new file, do layouts in the brand new file default to right justification?
In exploring your suggestions I find that the real issue is that when you use the Field Tool to create a new field, the field is left aligned but the field name is right aligned. This is obviously best arrangement for fields in a column. However, to re-arrange fields in a row (for viewing in list view) most of the text names must be changed to left aligned for them to align properly with text data. It would be great if there were a setting that would allow temporary change the default alignment for the text names.
FileMaker 13 has such an option with its new field picker tool (which also stays open so that you can use it to select and add multiple fields to a layout much more easily than the Field Tool that is your only option in older versions.