I don't think you are doing anything wrong by upvoting some well-written articles. Quite in contrary! As well, I don't think it's hurting you or your reputation. From my understanding, voting doesn't work that way either the reputation score.
However, personally, even if it would be so, I would keep voting and support what I like, and that doesn't give any exclusive advantage to those with higher reputation. Even more, I would fight against such rule if it exists.
Frankly, I don't care about the reputation score number above someone's profile if the article is for what ever reason good, interesting, entertaining, helpful, educational and well written in front of my eyes. Same, as I don't care how much that person earned so far or not.
If it's good, it's good - and I will reward it best I can.
Thanks for the comment. I will continue to vote on stuff I like. I have written a few articles that took me hours to research, so I know how much effort some of these great articles have put into them. Following.