I apologize if anyone has done this already (I couldn't find it), or if it's not allowed (please let me know!) but I thought I'd translate the comments on his images (using Google Translate, but it's better than nothing... I only know Japanese, but I'm clueless with Chinese! lol) Clearly a Chinese speaker could do better, but I'll do my best here. Not all comments are from before his arrest. Warning for profanity
First is this one... from bottom to top (in chronological order)...
* the first either says, "In the end, you're not the rapist, ah?" OR "Big brother, the rapist is you in the end, ah?" [obviously very different meanings... need a Chinese speaker to figure it out I think]; this one was posted on July 6 at 6:29am, interestingly 3 days before YZ went missing.
* the second says just "murder!" in English, posted on July 6 at 9:44am.
* the third says "F... Y" with some emoticon, and the fourth post, by the same user, says, "
... Oh, good gas, English is not good, don't know how to curse other than F"; the next post is also by them, "Just go to feces... *******" again with emoticons, which makes it seem to be joking [I assume "go to feces" is a metaphor similar to "go to hell" or "kiss my *advertiser censored*" in Chinese]... these posts were made between 10:02 and 10:14am on July 10, the day after YZ went missing.
* the next two posts, by different people, are in English, "That's Not Cool" and "**** your *advertiser censored*, murderer" made July 13 at 10:57pm and July 14 at 8:12am respectively [note these are still well before he was arrested]
* the last one says "murder" in English followed by "Murderer, look to see, what you see, the mother died". This comment was made July 17 at 1:20pm.
Next,
http://steamcommunity.com/sharedfiles/filedetails/?id=738881192 -- the only comment there says something like "I would like to call you every day" with an emoticon in the middle. The comment was posted at 10:05am on July 10 (I believe I'm seeing these times in EST, as this is my time zone).
Third,
http://steamcommunity.com/sharedfiles/filedetails/?id=742656610
* first post says "Brother kidnapping is not fun" on July 5 at 4:54pm
* second has an emoticon, then "Good gas" [this seems to be a Chinese phrase meaning something is fun?] at 10:04am on July 10.
* third says something like, "Actually, the message wasn't brush burst, not been accused of burst is also powerful. Want to be kidnapped, also safe~" posted at 3:05am on July 13.
* last was "Amitabha, here a tour," posted on July 16 at 9:34pm. A quick google search of Amitabha shows that it's a celestial buddha. I don't know anything about Buddhism so I can't comment further, haha
Fourth,
http://steamcommunity.com/sharedfiles/filedetails/?id=781021094; both comments are in English.
Fifth,
http://steamcommunity.com/sharedfiles/filedetails/?id=882671100, only comment is an emoticon followed by "If the death penalty", posted at 10:04 am on July 10 (I'm noticing a lot of the posts by this user were at 10:04 am and thereabouts)
Sixth and final image,
http://steamcommunity.com/sharedfiles/filedetails/?id=886845005
*first post says "To kill the murderer", posted at 7:13am on July 6.
*second is just an emoticon and "G…H", posted July 10 at 10:03am
*third comment is "Murderer, your mother dead, your dad, you, your mother out of leucorrhea abnormal, your mother tragic death sewer" posted July 17 at 1:18pm [is BC's mom dead or is this just a reference to a game? I'm just wondering because an earlier comment mentioned his mother being dead]
*fourth comment just says "I WILL KILL YOU" with a crow emoji on the left and a knife emoji on the right. Posted on July 17 at 10:41pm.
Just as a disclaimer, I know nothing about the games depicted in the images or whether the comments are about the game or not. Regardless, the content of the comments is interesting (and disturbing IMO)