There can be confusion between a parenthetical phrase preceding a noun phrase subject and a parenthetical phrase following a noun phrase subject, when the parenthetical phrase is a noun phrase.
- An expert philatelist, John Smith correctly identified the postage stamp.
- (An expert philatelist is a parenthetical phrase, and John Smith is the subject.)
- An expert philatelist, John Smith, correctly identified the postage stamp.
- (An expert philatelist is the subject, and John Smith is a parenthetical phrase.)
Careful attention to pausing is important.
There can be confusion between participial expressions in sentences like these.
- John Smith, being an expert philatelist, correctly identified the postage stamp.
- (John Smith is the subject, and being an expert philatelist is a parenthetical expression.)
- John Smith being an expert philatelist, William Brown showed him the postage stamp.
- (John Smith being an expert philatelist is a parenthetical expression, and William Brown is the subject.)