When Captain Harville and Anne Elliot discuss whether men or women are the most inconstant in love the camera continues to switch between a closer shot of the two and a more distant shot to include Captain Wentworth. In one of the more distant shots (while Captain Harville discusses the feeling of leaving behind family) you can see Anne is the one speaking however Captain Harville's voice is heard.
While clearing out her things at Kellynch near the beginning of the film, Anne finds a paper boat tucked inside a navy list. If you look closely, you can see that the words written on it come from the letter Captain Wentworth writes to her at the end of the film. It says: "You pierce my soul. I am half agony, half hope. Tell me not that such precious feelings are gone for ever. I offer myself to you again..."
At the dinner at the Musgrove's, the Musgrove girls read from the Navy List that the Laconia is a 74 gun frigate. Frigates of that era had at a maximum around 44 guns. A ship with 74 guns would have been a "ship of the line".