While it seems that link building becomes more difficult with every Google update posting comments on blogs and forums may still bring in more website traffic. Should a company engage on theses activities?
It's true that link building has become more difficult and the game has continually evolved. Back in the earlier years of my SEO career we used to engage in comment posting on blogs and forums as a way to get backlinks easily. We no longer engage in these activities unless they're under very specific circumstances.
First and foremost you never really want to have the attitude of "let me try to manipulate the search engines". You may not get caught tomorrow or in a month but eventually it will catch up to you and when it does the amount of work trying to lift a manual or algorithmic penalty is simply not worth the risk. I am mainly talking about people who use this as their primary means of link acquisition.
On the other hand there are cases where it's OK to do it. But it should be approached with a different mindset. Your thoughts should be somewhere along the lines of: How can I post a thoughtful and substantial comment that will provide clear value to the readers? If you do this and other site visitors find your answer actually useful, then having the link could provide some value as an interested user or potential client might follow it to your website. If you are doing this with a purpose that's other than just link building there could be some benefit. I wouldn't do it in any other case.
Any company that is just trying to get links to their website is not looking at the long term big picture. The best way to earn links is by doing real company stuff. You want to earn natural links and diversify. Sticking to one method is not a good idea.
Now for some practical advice. For example if you donate to charities they might provide a link back to your website. If you offer a scholarship for students, .edu domains will be willing to link to you. Sign up for HARO and respond to as many interview or PR requests as you can. If you host events there are tons of opportunities to list the event and link back to your website.
The most important thing to remember is that your anchor text should be natural and its quality over quantity with links.
According to Google's head of web spam team, Matt Cutts, Guest posting is not useful anymore. Here's their official take https://www.mattcutts.com/blog/guest-blogging/ .
I think forum posting and blog commenting is still effective, the only problem is, people don't often do it the right way. Let me share one thing about forum posting. If you join a forum related to your product and you post a lot of messages (relevant and useful only) and your account is not brand new, it has passed few weeks or months, then if you post a backlink to your website (at an appropriate place and in an appropriate way) then neither forum moderators would mind it, nor would Google. And if you just joined the forum today and you write a signature like this "Hi this is very good forum. Thanks. www.BlahBlahBlah....com then of course it's more than a spam.
Do you people know, last month, I was quite nervous, that Google says everything is spam. So how we should build natural links! Then I did my research, I didn't work for 2 months that time, since I wanted to discover something new, then I figured out the natural way to create Google friendly backlinks.
With those, we can compete with big brands in any industry as well.
Posting on blogs, forums and articles is beneficial to your SEO strategy only when done with the idea of providing value in mind.
If you are just posting just to get more backlinks for your site, then that is where you are going wrong and why you feel that is it not right move. However, if you are posting to add another point of view to the conversation or to provide helpful information, then commenting is a great strategy to use.
The right way to use comments to use them only on topics that you have an in-depth knowledge of. Otherwise the comments may come across as "me-too" or irrelevant to the conversation.
There are additional benefits in terms of content marketing for using such comments. I would be happy to discuss this with you during a call.