I've seen multiple of my answers get a lot of downvotes even when the asker marks them as the correct one that worked, they are completely grammatically correct, address the issue fully and are, imo, good answers. Yet they get like 3 or 4 downvotes and so do the questions. This has happened a few times and I really want to know if there is anything to guard against people downvote trolling good answers or downvoting other answers so theirs appears first.
So, lets look at some real data, answers of yours with down-votes, that are in the negative votes:
Most recently: What are the difference between Unity and Ubuntu GNOME? A duplicate question, on the surface the answer looks ok but immediately notice - One paragraph - No capitalization of product names - run on sentences - a lot of conjecture, no sources. And the first statement is technically wrong: https://askubuntu.com/a/115160/47291 Poor question and a answer that needs lots of help - It's a new user so they just accepted the first thing. I personally didn't down vote that, but I can see why it would attract downvotes, and the more you comment on it the longer it stays on the front page for all to see and attract more downvotes.
Next: https://askubuntu.com/a/512624/47291 , Ok, maybe... but he did say "I then selected the USB drive in the boot options." in the question. So the answer is short, and clearly ignores what the user already stated. I didn't down vote this one either, but I can see why someone would.
https://askubuntu.com/questions/505137/upgrade-ubuntu-12-04-lts-to-ubuntu-14-04-lts/505172#505172 This one is well explained by the(apparent) downvoter.
What are the risks if install a secondary desktop environment / interface on my ubuntu? Don't assume that someone will edit for you, or even care it was edited when it is also not technically correct. The other answer is right in that multiple desktops will cause random strange problems.
Dual-Boot issue (and much more...) no capitilization, no steps, you just told him what to do in one rambling sentence, not how to do it, then when he has problems, you say "google it", then you ask why someone downvoted? I'm surprised some of these don't get more downvotes. Also, I didn't downvote this one.
https://askubuntu.com/a/489714/47291 yes, that is why there is a "Off Topic" flag and close vote... everyone already said that in comments. I didn't down vote this.
https://askubuntu.com/a/489020/47291 Downvoter(apparent) clearly explained, answer has information that seems to be wrong, and no sources to back it up.
https://askubuntu.com/questions/498278/why-does-linux-ubuntu-have-better-wifi-connectivity-than-windows-xp One run-on sentance, no capitalization, and no sources for a very surprising statement. I did not downvote this. But it is clear why someone did.
And that is only Answers I'm looking at, as you asked if someone is trolling your answers, and the clear answer is - no, you just have a string of answers that are of poor quality. Also I didn't list any that were balanced zero or had positive votes, because ultimately the upvotes are worth more points.
Sometimes answering dull questions also make your answer dull and if you do not explain it clearly (if there is some obsolete things etc) you are downvoted. Remember one thing, at least 125 reputations give you the power to downvote. Suppose a user asked "What is Ubuntu? " and you answered "It is a Linux distribution". The user may accept it but both of you can get downvote for this dull conversation.