For a situation not to use d/f lk. ^ Man, I have a Rufus on my buddy list who would corner me with his scary dive kick pressure then rape me with his scary dive kick pressure in the corner. :_: I finally leveled up fighting him one day and started using cr. hp os tech and it COMPLETELY turned the match around. His counter-hit set-ups were way too tight to catch me pressing buttons (online meta-game of jab mashing can be rough on tech traps ) AND I was actually teching throws with it. So when that didn’t work, he adjusted his dive kick heights, but his pressure just wasn’t the same. It was awesome.
I am one of those Chuns who don’t really care about charge when it comes to footsies. Often, I use st. mk (or j. fierce, or j. mk) when I am walking forward, or when I have JUST started to walk backwards to throw a fireball, or right after I throw a fireball so whatever, I can charge after I anti-air them if I really want a fireball.
BUT d/f lk is better than st. mk in almost every way except for meterless damage. You can juggle ultra even on trade; eat your heart out Ryu. Dash ex legs makes up for damage and gives you a knockdown you are super familiar with by now. You might even be able to stomp if you d/f lk if you do it low enough (I am stingy with meter). The only thing st. mk is better for is that it automatically cl st. mk for you, which is great vs crossups (but it fails in situations where jump back fierce is the better option).
I was playing vs a Zangief, and you know how he likes to mix in between jump fierce and jump mk. Jump mk is a bitch to anti air, and it beats or trades often. Same with jump fierce, but less good. St. MK trades way too much, but d/f lk beat those things CLEAN with the same timing as st. mk.
In conclusion, if you are using terrible anti-air choices to keep charge, d/f lk is the anti-air for you. What better time to charge than when your opponent is knocked down?