@MassimoOrtolano I was a frequent user of Usenet news groups, such as sci.math, comp.sc, etc. since 1990. There was a morning in 2010, when I got on comp.sci, every post on the main page were spam posts, there was no single one that I would read. I went to sci.math, not much better. Then I saw a post which mentioned MathOverflow, I went there, immediately loved it. Then I joined MO, Math, TCS SEs. a few months later, Academia SE started beta version. I joined it. Then became a frequent visitor.

One of the differences between Usenet and SE is that, there was almost no spam posts because SEs are moderated by moderators and self moderated. This is why I have become a spam killer because I don't want to see SEs become another Usenet network in 2010.

Yes, I know spam flag causes heavy penalties. Many years ago, I was unsure about a spam post in a similar way. I asked a question (I don't remember how I asked (on chat?). Aeismail replied "Spam is spam, pure and simple".

But, later I found out not every mod has the same attitude. So, I became conservative. Both Strongbad and Wrzlprmft sent message want me to flag more, I did not do so because declined flags gives me bad feelings. I hope mods now understand me better now.

@Wrzlprmft Also, I would like to take the chance to thank you. You were the one who introduced me to Charcoal HQ Chat room. I learned many things from that chat room and accumulate many flags on many SE sites, e.g. I have more helpful flags on SO than on Academia even I have no contribution on SO except the flags.

@Nobody I understand the feeling because I was a Usenet user too, since 1995. Actually, there are a few users around SE who I first met on Usenet back in those days.

I even met someone in person or have acquaintances in common.

@MassimoOrtolano Yes, I recognize users on SE sites who used to be on Usenet.

@Nobody I don’t remember doing this, but you are welcome.