Don't give out your email randomly and don't open spam from people you don't know. Beyond that... take your paranoia meds. There are dozens of ways someone with a lot of skills my hack your PC. But don't get too full of yourself. Hacking one single poster because your don't like a post is like punching a single raindrop because the rain is hitting you in the head. No one woud do it because it is a waste of time. You are more likely to get hit by a drunk driver. Relax.
The long and short of it is: Yes, it CAN happen. It is also the least likely exploit system to work, as there’s seven different flavors of ADS. You have only the same permissions as the enacting function; not like a payload program that is in the startup sequence. It is the least functional place to do it as well, as other exploits allow you access to all of the filesystem.
Does this make it useful for a hacker to exploit? Maybe - to target a specific machine in a specific location with a specific attack, knowing the flavor of OS and everything else, it MIGHT be a useful vector, but it would also be the LEAST useful vector. At some point you’re going to be transferring from your payload program to the ADS datablock, and that’s where the virus scanner will pick up the code.
Honestly, rather than mess with this stuff, I’d certainly put Linux on a USB dongle, boot up the computer in Linux, and then e-mail any and all critical files to an email account, and then reformat and use a more secure OS.