Hi. You need to look at the details
1881
2 Avenue Cottages
Richard Reeves head mar 73 shoemaker Kent, Deptford
Elizabeth ditto wife mar 60 Kent, Sandwich
1891
Ditto Cott [the top of the column says Avenue Road and then the addresses are e.g. "Ditto, 1 Cypress Cott" do the Ditto refers to Avenue, making this Avenue Cottages I think]
Richd E Reeves head widr 83 general dealer Deptford, Kent
Eliz. A ditto sister s 70 Sandwich, Kent
So I would say that it is the same Richard - same address, same age, same birthplace.
Not sure about Elizabeth. Same age, same birthplace.
Maria was 55 in the 1871 census so this might be her death:
Deaths Jun 1879
Reeves Maria 64 Edmonton 3a 153
Richard may have entered "married" out of habit in 1881 and Elizabeth could have been his sister there too. Did he have a sister Elizabeth/Elizabeth Ann?