How does one tell if sads are honest or not? I've never really noticed "fishing", myself.
It's not like you gain much from fishing anyway. About the same as you might gain from posting a real sad feels: comforting words from people off the internet who you may or may not even know in meat space. In a similar vein, you gain nothing really from knowing whether a sad post from some stranger on the internet is real or not. So why care in the first place.
EDIT: Ontopic sad: I feel like "friends" are a fake concept to use on online interactions. Sooner or later they decide that you're not important to them at all and they move to greener pastures. Isn't it ironic that the technology built to help people connect and communicate more easily also makes it seem more normal to abandon people and dehumanize the people you talk to, making them just mere entertainment?
I don't know anyone on these forums in real life, as far as I know. None of you know me, really. From what I know of most of you, you seem like cool people, although maybe you're all secretly lizardmen or mantises or everyone's actually Descan. I wouldn't rank any of you "friends" in the same way as I consider meat space friends as "friends" but I still respect you all as people and generally wish you all good feelings. Which is also how I feel towards real life friends and acquaintances.
That being said, due to some anonymity and the potential requirements of real life taking priority over internet stuff, it's likely that given a choice over real life or internet, a person would choose real life and "move on".
Or their interests would change and they'd "move on."
Or they'd feel too guilty from making an ass of themselves all the time and burdening everyone with their nonsensical and unimportant opinions while contributing nothing to the online community and silently slink off into the night and "move on."
It doesn't change how the forum and interactions with the forumgoers had at least some impact on their lives.