Sorry for necroing, but I have experiences similar to another user above. I'm just a lurker here.
He knew/met me from my Deviantart days. Stupidly, I put my age in my account description and he knew I was a minor. I was nowhere near incredibly popular on there but I met a lot of people from it. I think he commented on a journal I made at some point? That was back when I was 14. I jumped ship from dA to tumblr (like a lot of people did back then) and he followed suit, that or he already had a tumblr in use at the time. He was a part of the 'anti sjw' crowd on there for the most part, but still considered himself a commie and producing pretty much the same content as shown previously. I don't know if I realized how old he was at the time, and to be honest I interacted with a lot of people way older than me that I shouldn't have.
We both followed each other on tumblr and he took a liking to me (now I know why) and whenever I'd reblog anything with shoes or outfits (I would post Japanese fashion content a lot) he'd always link it to me on Skype and said 'your feet would look really cute in these c:' (the above user is correct about that specific smiley, it's fucking nasty for me to look at now) or something of that nature. Normally it'd be something about feet, but he'd reach out and even do it with lingerie photos at certain points, which was also fucking weird. He'd also comment on photos of myself, including when he and I added each other on Facebook later. He knew my age, at this point I would've been 15-16. A lot of his "friends" online were minors of either sex, I didn't interact with many others he knew though. Once, he even caused an upset in a groupchat that a few friends and I had because he insulted a certain franchise an old friend of mine enjoyed, and it was awkward from there on out. Another underage girl he was "friends" with that he introduced me to was in that groupchat too. At one point, he also asked me if he was misogynistic or if I creeped him out, and I genuinely didn't know how to answer. I should've blocked him right away then, but at the time I didn't think that it was a huge deal. He also had a habit of calling underage girls who didn't want to talk to him anymore bitches and would start complaining about them to others, as if we couldn't understand why. I don't have screenshots of this because I don't have access to that Skype account anymore, however it lines up with what was stated above. He also used to work a lot of fast food/minimum wage jobs that he'd constantly complain about, namely Papa John's. He probably worked those because he couldn't do anything more advanced or strenuous.
I remember that tumblr callout circulating, and I regret staying silent. It's been deleted now and that's probably because the owner of the blog deleted the whole thing entirely (as is par for the course of the majority of sj/"discourse" bloggers at that time). I also recall him being super anal about Newgrounds and hating any videos that were from Newgrounds. I don't know why he was so upset about it, but I think it's kind of funny now.
He added me on Facebook and unfortunately I accepted, though I still tried to keep my distance. He messaged me all the fucking time, I had two facebook accounts (one I lost access to and he added my new one) always trying to start up a conversation. One string of messages is just him trying to initiate contact with me over the course of weeks when I didn't reply. I don't find this to be creepy/predatory inherently, I think he really was desperate for any sort of communication at that point, but he knew how old I was and that I was nowhere near interested. I've had him blocked for a little over two years now and it's been freeing, and he hasn't tried to reach out. I don't know if he just doesn't remember me, or if he's hurt by being blocked, or if he thinks I just deleted my account. Either way, it's been quiet and I'd like it to stay that way.
TLDR: he specifically commented on the feet of underage girls, wouldn't leave them alone and bitched when they told him to fuck off, would add their private social medias, generally just complained about things no one cared about, would ask us to defend him if he got in arguments with other retards on tumblr/dA/whatever, made little to no improvement on his life at all and only kept up being "friends" with underage or barely of age people.