The title "Double-spaced," Skinny's broken spacebar, and the fact the sentences are arranged in pairs are all clues to the mechanism of this puzzle: Signmakers. However, there is a twist to these signmakers. One word from the first sentence in each pair is shifted to another location in the second sentence (hence "but at least the shift works.") Enumeration is the number of words in each sentence.
Form a [synonym] to rig in a lissome set. / Format; original is so mes[sy, no NY M]et.
I saw hack on Earth, [and] a truss ires single gal. / Is a whacko near that Russi[an D]ressing legal?
Banal [anagram] or rec. over time? / Ban a Lorre covert, I me[an a gram].
A son [of] Eleanor dealing, and his insistence real. / As one lean ordeal in Gandhi sins, I s[of]ten cereal.
Can [only] that chap resent a tire? / Can't hatch a presentati[on ly]re.
"The red [word] is maybe," lie forgiven ogre engineers. / There dismay belief, or give no green GI ne[w ord]ers.
Outwit [to] have tabs or base narrow. / Out with a vet, absorb a sena[to]r row.
DEA convened; if I [slide], esters echo ruses. / Deacon'[s lid e]ven edifies terse choruses.
Scar lets [left] end of forgotten orchestra in. / Scarlet sendoff, or got tenor c[lef: t]he strain!
The shifted words are "Synonym and anagram of only word to slide left." 'Slide' is the only shifted word that moved toward the left in this puzzle, and the word that is its synonym and anagram is SIDLE.