Being someone that loves to honor him with trying to win awards in his name, for him, I still think that it should come down to personal preference and that nobody should be guilt tripped or made to feel they did something horrible or immoral. At the end of the day, he's already won awards on his own merit, and while it's a nice gesture, he already knew how much fans supported and loved him before his passing (and I'm sure wherever he is still knows and sees how much people care about him and support him, even if they aren't voting for him in a contest or award voting deal).
Winning awards isn't the be all end all - and groups like SHINee, and the members individually, have proven this time and time again. They have all been against groups that (in my personal opinion) were lesser in terms of talents but still easily beat them for awards for whatever reason you can throw to stick at a wall (popularity, hype, bandwagon, fandom size, different tastes in music etc). It doesn't mean those that won it are "more deserving" of the award, nor does it mean that not winning the award somehow puts down those that haven't won (and on the same token, it doesn't mean that those that won didn't deserve it or earn it, etc).
Winning awards is just a physical manifestation of "you have a lot of backing" regardless of music quality or the people making the music.
That all aside, it's really horrible to make someone feel guilty, to hate on them, or label them as immoral or messed up for not voting for someone, solely on the principle that they have passed away and "we should get them an award!" Sure, Jonghyun's got amazing music and I personally vote for him 9/10 (though in the case of having to vote for him or Taemin, I will be sitting out, because I don't usually vote anyway and for me personally it always has felt weird when two solo members of the same group are up against one another), but that doesn't mean others will agree with me - and just because he's eligible for something at the same time others are doesn't mean that the others should be shut out simply because "well he's passed and we will ignore the chance for others to get it because of this" - no. I feel he would never have appreciated a "sympathy" award (even if it's not out of sympathy but to honor him in a way) - if someone wants to honor him, support him, show the love? Donate to his mother and sister's charity they created in his name to help youth similar to him, "Shiny Foundation."
Voting for who you feel is the best or who you enjoy the most is what matters in these types of things. Quality does not matter. Music styles do not matter. These are all things that are different for each of us, and as such will lead us to vote differently - you shouldn't feel obligated to vote for someone based solely on a dark day in his 27 years of life.
On the same breath, it's a sweet gesture and one that I support if someone wants to do it. I know I've pushed to try getting those that weren't planning on voting, or that were Shawols to vote for him in order to try winning him an award that I still feel he deserves (for his music, not for the circumstance that occurred). But I won't make those that don't feel that they are somehow in the wrong.
Sorry that was long. I just feel very heavily in matters such as this.
God rest his amazing soul.