I'm working on a blog website and I doubt about forcing users to create accounts to post comments under my blog posts. What is your opinion about this? Is it good from User Experience Aspect?
The single bad thing about Comments is Spam.
Once your blog starts to get active users, many bots will try to spam the comment section with useless posts redirecting to malicious websites. This is a serious issue since it will also lead to deterioration of your personal brand with such comments and some might post negative comments which aren't constructive.
I think Account creation for comments should be mandatory and can be easily handled with Disqus and other comment signups which only require you to add a plug-in. And people who read blogs frequently generally have these accounts enabled.
I'm not entirely sure if you want them to create an account on your website or something like Disqus, but I feel comment section is one of the sections of the website that is generally ridiculed with fake links and unnecessary comments so precaution is always appreciated.
This is one reason why Youtube switched from usernames to actual Google+ names and better comment sorting to reduce spam and negative comments.
There are another aspect not mentioned in the accepted answer.
In some countries, the owner or administrator of a site may be legally responsible for comments left by anonymous users if the judge considers that insufficient measures have been taken to prevent or eliminate defamatory comments inciting racial hatred, violence, etc.
In Spain there was a case of a singer that was the subject of several defamatory and insulting comments in a web site. The justice found that the site owner didn't supply correct contact data and allowed the users to post comments without any kind of control (those comments included insults, personal data of the artist, beheadad photos, etc) El Supremo confirma la condena a una web por sus comentarios sobre Ramoncín SPANISH
The Supreme Court (TS) has confirmed the condemnation to the administrator of the page XXXXXXX.org to pay 6,000 euros to the singer XXXXXXX for meddling in his right to honor by holding this web responsible for the vexatious opinions expressed by various Internet users against artist.
The condemned appealed this resolution when he estimated that the person responsible for the expressions appearing on the web should be the user who made them and denied that he knew of the unlawfulness of the opinions and comments sent by users until he received the demand of the singer.
The ruling explains that the Services Law of the Information Society and Electronic Commerce establishes that the providers of accommodation services or storage of data will not be responsible for the information stored provided they do not have effective knowledge that it is illegal or, if have it, act diligently to remove the data or make access impossible. In this case, explains the ruling, the service provider "has not fulfilled the duty of diligence in order to detect and prevent certain types of illegal activities."
The ruling also explains that the owner of the website provided an address "inaccurate or at least not current" to the corresponding Registry, which prevented Ramoncín communicate with him in an easy and direct way to interrupt the dissemination of expressions and photographs that were harmful to him.
He added that access was allowed to third parties to that page until XXXXXXX went to court in defense of his interests, "thus not observing his duty of diligence in the rapid withdrawal of illegal data or in preventing access to them ".