The answers to the 13 puzzles are, in order of puzzle posted:
Consecutive Vowels: I WANT TO BE TOUCHING YOU
Chess Enlightenment: KNIGHT TO BE ONE WITH NATURE
Island (sketch): EXILE
Labyrinth Puzzle: MIDNIGHT
No Pun Intended: SUPERINTENDING
Listen to Yourself: EUREKA
Real Programmers: SPACETIME
Arsenic Based Life: AS YOU LIKE IT
Iambic Pentameter: PROSTHETIC FEET
Self-Description: THIS TEXT IS THE ANSWER
Five-Minute Comics: Part 1: UMMM SOME CREATIVE PUN OR SOMETHING
I Don't Want Directions: LOST FOREWORDS
Five-Minute Comics: Part 2: MATRIX FIGURE
The meta connection is:
Each answer contains exactly one occurrence of one of the letters X, K, C, or D. Each instance appears at a unique place in the answer, from 1st to 13th. (That is, for one answer the XKCD letter is first; for another answer, it's second; and so on.) This provides an ordering for the answers.
Using this to extract an answer:
In this order, the answers are:
. K N IGHTTOBEONEWITHNATURE
.E X I LE
.MI D N IGHT
.SPA C E TIME
.EURE K A
.MATRI X F IGURE
.THISTE X T ISTHEANSWER
.ASYOULI K E IT
.UMMMSOME C R EATIVEPUNORSOMETHING
.PROSTHETI C F EET
.SUPERINTEN D I NG
.LOSTFOREWOR D S
.IWANTTOBETOU C H INGYOU
The letters after the XKCD letters spell the message "NINEAFTERFISH".
"NINE AFTER FISH" indicates that we should start at the XKCD comic titled Fish, which is #1377, and then go nine comics forward to #1386.
The final answer is then a panel from this comic.
Final answer panel:
Since OP is a nice person who wants to reward their solvers, I expect this is the final answer:
A wonderful reward for all of us here at PSE! May we continue to share our wisdom with all. I haven't prepared a speech for accepting this reward on behalf of the community, so here's a list of Thank-Yous.
Special thanks to Deusovi, Thomas Blue, Bass, ffao, the PSE Community (esp. Bass), noedne, Persona, phenomist, Sid et al., Alconja, Deusovi and SKOG, Deusovi and Level 51, and Deusovi and phenomist.
Super special thanks to the OP stacksfiller for creating this quite simply astounding meta suite in just two weeks, and all within the Fortnightly Topic Challenge!