Regarding the reputation part - first of all, you misunderstood the comment if you think Gill was hostile at all. She was not, and it is not negative towards Lin Dan in any way.
Secondly, any competition where you actively play against an opponent (rather than the clock, or any measuring device) has a substantial psychological component. In this case, that means that through years and years, LD had built a reputation of being unbeatable. He had staged some great comebacks, he had utterly smashed opponents, he had toyed with some - done it all. Only a select few were able to beat him, ever, and apparently no one was capable of it when he truly wanted a title, and his many major titles seem to support that hypothesis.
Now even LD is not immune to age and its effects, and he actually started changing his game bit by bit as early as 2011, in fact I see a very clear difference between, say, his 2010 Thomas Cup play and his 2012 OG style. While he didn't have a huge drop in performance, his level did decline a bit compared to his previous heights, the 2007-2009 Era probably being his peak and the best anyone has ever played MS.
That did not, however, change the fact that everybody he played against knew that he had won it all, that he had beaten everyone, and that he was, for years on end, seemingly unbeatable to mortals, only losing a few choice matches here and there to elite players. Others, being outside of this elite, never dreamed of defeating him because he appeared to need a weak day to be beaten by the World number 1 (or 2 or 3), what chance did they stand?
It's very much the same when you play in a club that has several teams, and you're in the 3rd or 4th and play the best player of team 1. You haven't played him before, but you've seen him destroy others who in turn beat you. You've seen him toy with guys who have barely lost a game to you. Now, after months, you play him. At first, it's a match like any other. You even lead by 2 points at one stage.
Then, all of a sudden, he ups the pace. He starts attacking more, intercepting and smashing shots he previously took late, and moves a lot quicker, taking your shot earlier and putting pressure on your drop shots even. You start to fall behind. Once he has established a 5 point lead, he pets up a bit - but his play is still at least as good as yours. You know he could, at any time, start killing your drop shots again if you play them loose, so you reduce your margin of error. He returns some of your smashes that never came back before, so you start aiming for the lines, still playing them as hard as possible. Yet you don't catch up, no, the gap is widening. You think: this is why no one beats him. How can I possibly do this, when all those better players have failed? You fight a bit less for each point. You start losing a bit of body tension, your reactions get a bit sluggish. You lose 21-14, 21-7. You remember this the next time you play him, 4 months later...
PS sorry for the positively massive post. Didn't realize it was that long whilst typing