Just putting an url without any relative topic comment could be considered as spam,,resulting ban of your site Comment only either if you read whole topic and understand what they trying to say or you have any special or relative idea concerning the topic,It can help you a lot
If you don't understand the topic don't post a comment you'll sound like a spam or you can research first in order to participate in the comment discussion.
Don't spam, don't use any software to do auto commenting. Try doing manually commenting in relevant web sites or blog, you'll get good traffic too.
If you find relevant do follow blogs and leave a well written comment, not spam. It can be beneficial to your link building process. But you should never spam people's blogs, forums or anything else.
I don't mind people using a keyword-rich username with a link to their website as long as the comment is of a high quality. Anything less will be deleted.
if you are using automate tools to post comment.. then it's 100% spamming.. but you could go to blog that have relevant content.. and give a sincere comment based on the topic.. now a lot of blog dont pass the PR but it can help your site to be indexed..
What about this problem... The comment is ok, but the site they link to falls into one or all of these: 1) In a language other than my blog 2) Totally unrelated to my blog. Let's say my blog is about SEO and they link to their tennis shoe eBay site (some of you should know what I'm referring to). 3) A new site which has just been established, and looks poor quality. The chance is it could be pulled anytime into a parked domain. What would you guys do?
Let me put it this way, If you don't "spam", your competitor will do it. And if he doesn't spam he WILL buy paid links. Thats the only 2 ways people get to the top nowadays. Ive seen all sorts of companies spamming, from top web hosting companies all the way to Drug rehab centers. Most webmasters won't consider what they do "spamming" though , i.e dropping long descriptive anchor text instead of your name on dofollow blogs or dropping links on abandoned blogs and forums (cause they figure the site is abandoned so what does it matter). Its all spam when you think about it, cause you wouldn't do it if it wasn't for the link or if they didn't let you use descriptive anchor text.
I do not think it's just solely about comment quality. The site you link too from your comment needs to be related to the site you comment on, and of some quality at least. A good comment but a junky site....nobody has talked about this yet.
If you just leave a good comment in a blog then it is good, but if someone start spamming with blog commenting, then off course that is bad.