I too pay to play this game the way I want within the ToS, and if I don't feel obligated to answer other players "Hey, are you there" while training, or resource gathering than I won't. However, when I get pulled away by a gm because I didn't feel like socializing with you, expect to get a Harrassment page in return.
How hard is it to stop and say hello? Especially if the player persists in waiting for an answer? If you are willing to spend the time to place a harrassment charge after a GM shows up, perhaps you need to reconsider what you are doing.
Wouldn't it be quicker to stop for a moment and to
say hello and NOT waste the Player's time, the GM's time, and YOUR TIME too.

Say something to let anyone interested that you aren't an unattended macroer. Seriously, how hard is that and just
how many players care enough to bother to ask if you are THERE?
..
..now back to real life ..
While I follow you and understand what you're saying, please keep in mind that for me personally, if I am training a pet or doing some other tedious activity it means that I am unable (at that time) to socialize. While I may be at the computer, I may also be on the phone, making appointments, or caring for a sick person, or some other activity that makes it a hassel for me to answer a would-be UO policer. (Maybe I'm just watching a movie)
Yes I am at the computer, watching my character, not afk... But no, I may not be able to have a conversation with someone, answer them right away, or even feel the need to justify my actions (dependent on who is doing the bugging). If someone comes along and wants to use the shadow ele too and says something polite like "mind if I..." that person also has a bigger chance of getting a response out of me. Not only do I know they're not there to chat, but I also don't feel policed.
If I had time to chat and socialize, I'd be doing something else with my guild or alliance and not doing the tedious macroing type activities this game requires to be able to play (ie: pet training, pot making, ingot gathering).
I think this applies to more than just myself.