I'm not even sure what "tag" icons are either. I assume you're referring to one of the two columns in thread view (see attached pic) - if so, the left ones (blue arrow) are called status icons, the right ones (red arrow) are called post icons.
Each of these serve a different purpose and are part of normal VB functionality.
The status icon's purpose is best explained by the table at the bottom of each page (see 2nd pic)
As for the post icon, the user decides what it should be or even if he wants one at all and are intended to show the tone of the content he's posting.
I think they both serve a purpose and should be left as is.
And Vlad - just in case most of the votes tell you to get lost - I would have to disagree with them
