Solution: Themes and Counterthemes
Answer: PARIS, SHELF

Written by Justin Melvin

First, solvers should notice that each column is in alphabetical order. By taking one letter from each column, one can form four items that are in a category. The leftover letters are one letter shy of another member of the category.

acids:
AMINO
EPTIC -> pEPTIC
FOLIC
FATTY
LEWIS

confectionery:
FUDGE
JELLY
LOLLY
NOUGT -> NOUGaT
TAFFY

fish:
CONGE -> CONGEr
GUPPY
SHARK
SMELT
TROUT

hot under the collar:
ANGRY
IRATE
IRKED
ROLED -> ROiLED
UPSET

taking a rest:
BREAK
IESTA -> sIESTA
PAUSE
RELAX
SLEEP

Taking the letters to insert gives the first answer (the 'theme'): PARIS.

To find the 'countertheme', note that there is another letter that could be uniquely added (and in the same location) to each leftover to make a non-thematic word:

sEPTIC
NOUGhT
CONGEe
ROlLED
fIESTA

These spell the counter-theme: SHELF.

Author’s Notes

It's a real miss we didn't respond with Marked as resolved when teams submit their second answer to English round puzzles.