Tricky one....if morally and ethically you are not hurting anyone, I don't see it as morally wrong...your boss might think of it as time wasting, and I think anyone who has access to a computer at work has played at times when they shouldn't have, especially if they are a writer...it is very hard to egnore the white space on word and the potential to put words on it and work on that WIP.
I can't answer your question, but maybe think about how your boss would feel. Jobs are growing scares in this time and age, and unless employed to play on the Internet, or type up your manuscripts, I would look at my motives for wanting to be employed with that particular company.
My reason for being employed by my employer was I was not confident enough as a writer to not be employed, and that industry was the closest thing or the only other thing that interested me apart from writing, and no matter how hard I tried to get away from writing fiction I couldn't but spent 16 tears writing computer programs that processd data, words....this did give me some type of satisfaction, that I could sit and still type...even if it was a different language.
Not everybody can do this though...but you do need to live, until you write that bestseller.
If someone is paying you to work, I personally think you should work at making that company to be more profitable...I think when employed unless offsite, you are working with other members of a team, and even then....maybe some of them need help getting something completed, and maybe they don't.
I spent sixteen years sitting in front of a computer while employed and the Internet was always available to me...I actually loved that job, but had to keep writing. My love was always writing, and I stayed employed because I needed the money to live. I worked until I had no work left, and no one had any to give me, then I played....naughty me, but I also increased my companies profit margin, so didn't feel quite so guilty the majority of time. I was quick, so I made sure we all got everything done, and when they went and had lunch at the pub, I stayed back and played with words.
I use to spend any free moment I had typing up my manuscripts, my lunch hour, the five minutes my boss was out off the office when I had nothing else to do, which was rare. I stayed back late so I could used their brilliant laser printers to print out my hard work that I had typed at home and in their time.
Final word, my high paid employement never made me truely happy, but it did allow me to live, and supported my writing addiction. In my own defence, I never really thought it was ethical or morally wrong to spend so much time doing what I was not paid to do, and I doubt it would be that easy to do in todays work environment as it was for me, but I never felt terribly guilty because I worked 12 hours a day and more sometimes to meet both their goals and my own.
I worked really, really hard for that company, even though I could not wait to get home to my typewriter. After a few years everybody there knew what I did, that yes, I spent every break I had typing stories, and I stayed back after hours and use their brilliant WordPerfect software, and printers, and they undestdood what my real love was, but they couldn't complain because I did do what I was employed to do.
Well once, one of my coworkers complained to our boss about all the photocopy paper I was using after hours because I was printing out my stories, and when I offered to pay for the paper, I was told in a very stern voice to not waste it
Not sure if this helps, but I see how you feel, and I am one who would never suggest you throw away your day job to write without an income of some kind that can keep you above the poverty line. I'm 43 and now write full time, but it took many years to get to the that point.
Maybe look for a job that can get you as close as you can be to what you really want to do. Pick the job you would want to do if you didn't want to write, until you spit out that novel that pays you the ability to give up that job.
Welcome