I'm not saying that Lightsworn is a bad example to use - it has clearly defined strengths and weaknesses, so it is easy to understand how to sidedeck versus such a deck, but cards such as "Leeching the Light" are terrible sidedeck choices period, and using "Shadow-Imprisoning Mirror" as an example for Lightsworns is not a great idea (because the card is useless the majority of the time in that matchup). Additionally, re:thought-provoking article, the article doesn't really educate the newbie on all of the reasons he or she is sidedecking in the first place. Two extremely important principles of sidedecking is that ideally, your sidedeck should cover as many decks as possible as well as serve as a "patch" of sorts against decks you have negative matchups against; neither of these is mentioned here, while you do spend quite a bit of time talking about cards that are sided against different decks (why not just use one or two decks consistently throughout the article as an exemplar?).
But quite a bit of my beef is with the fact that you used Leeching the Light and Shadow-Imprisoning Mirror (vs Lightsworn) as examples - this is likely to be highly misleading for any newbies who have read / are reading / will read your article. Yeah. (Soul Release is pretty bad vs LS too, actually ... but oh well.)