By deixis, I mean what George Yule calls " 'pointing' via language" (Yule, George. _The Study of Language_. New York: Cambridge, 1996. P. 130).
As this publication points out, there are a number of deictic expressions (person deixis, place deixis, and time deixis). Demonstratives basically serve a deictic purpose in that--as my classics advisor likes to say--they are "finger pointers" ("this" and "that"). Sometimes the demonstrative pronoun can be used to emphasize what has already been said. This is called "the deictic reference." On p. 596 (hOUTOS 1.b), BAGD says that hOUTOS may have reference "to [something] that has immediately preceded" with the implied idea--"this one." The examples given there are Lk 1:32; John 1:2; 6:71; 2 Tim. 3:6, 8; Jd 7.
"Nothing new is added in this verse [Jn 1:2], but two points are repeated from v. 1 and thereby given emphasis" (Morris, Leon. _John_ [New International Commentary] p. 78).