I always love to get feedback on my articles. From the corrections of my grammar to comments on the style and information of the article there is nothing more enjoyable to an author than to get feedback, except to get useful feedback. And there are a few things that make your comments on Helium far more effective:
1) Tell me what article you are commenting on
This is by far the most frustrating of the problems when getting feedback on a Helium article. No matter how useful your advice may be if I don't know which article you are writing about it is nearly useless. Try to remember that when you send a note to the author of an article that they aren't told which article you are commenting on in the email.
2) Try to say something positive
We all want to improve our craft and the best way to do that is to improve on our errors but that doesn't make it easy. The harsher you are on an article the more important it is to find something positive to say. Try to remember that someone put effort into this and they are far more likely to listen to your advice if you start with something kind.
3) Be specific
This is true both of positive and negative feedback. The more specific you can be the more useful it is. The easiest for this example is grammar. If there is a mistake to be fixed knowing the paragraph and sentence makes it far easier, but this is also true of unruly sentences. If there are confusing lines or phrasings in my work I want to know, but what I really need to know is what sentences are problematic, not just that they exist.
5) Be willing to talk
If a writer takes time to write back asking questions and you want to be truly useful then send them back a note. This shouldn't be a major issue for most people and it can mean a lot to someone who is just starting out.
It is worth mentioning the other types of feedback that are important to Helium as well. The rating system is useful for writers because it gives them a chance to compare their work to others on the same topic and see what is best received. The more people rate the better this system works.
The other major form of feedback are the flags. Flag inappropriate and Flag Plagiarism. These are the harshest forms of criticism on the site so try not to overuse them, but when it is appropriate they should be utilized.
Getting feedback on my work is one of the reasons that I use Helium, and the more effective the criticism the more I appreciate it, so try to remember the standard rules of critiquing and a few of the basic ways that Helium works and your comments will be both effective and appreciated.