Given that the user in question was trolling and had all comments reduced to very negative values, what most likely happened is that the user was banned. Sometimes when users are banned the most insulting or trolliish comments are deleted when the user is banned. Note also that all the comments are available here. Considering the level of insulting vitriol in the comments, outright deletion seems like a completely reasonable response. I don't think comments that say things like:
Long time lurker - why you even bother arguing with Cryonics people - they are a delusional cult, technophilliacs who barely understand what cryonics ACTUALLY IS but they are still selling it to others. Bwowk is one of the main guys in the cryogame who writes tonnes of litreture to twist up the heads of people with a 140 IQ and make them belive that they have made the right choice with cryonics. He has been doing it for years and years - Melody is not wrong about 1 million words
is at all helping the signal to noise ratio.
For what it is worth, calm, careful negative comments about cryonics are generally accepted. See for example my comment in this thread.
Deletion of comments by richiekgb is simply letting the eldest Billy Goat Gruff do his job.
Richie may be a troll, but there are those who seem to take him seriously and applaud his efforts. He doesn't seem to be a deliberate troll, just an over-emotional jerk who is genuinely upset about cryonics. I realize we need to have a filter in place to keep the SNR good, but I thought the karma system was probably sufficient in this case. I could be wrong though; I don't have any experience with moderating a forum personally.
A brief line from this comment indicates that the author of the cryonics-critical comment quoted here was perhaps not the one that deleted it.
Was it deleted by a moderator?
Honestly, the decisive downvoting seemed to do the trick of hiding it from casual readers who don't want to see the long annoying rants. I don't think it was casting any doubt on the credibility of cryonics.
While it sounds like the author regrets posting it, I would think they should be allowed to delete it themselves.
Edit: Originally titled "Cryonics critical comment deleted?"