When editing in-game maps, there are a bunch of things in the levels that are blue lines on the building windows. What are these and would it be okay to remove these?

You can't remove them.

I'm not referring to the gridlines. I mean the markings that look almost like scaffolds.

Um? Screenshot?

Those are the outlines of the brushes you have laid out (the blocks).
It may look very strange and overwhelming, but they are quite helpful at times. There is no way to remove them as far as I know.
However, if you look at the top left corner of any of the 4 windows, you can adjust the settings on which view you want. (ie, you can make all windows of 3d textured from different angles if you wanted)

Are you talking about the blue lines that show only in the 3d window? i.e.,
image
blue_lines.jpg
If so, you can turn those off by selecting "Map"->"Unload Portal File" in the file menu, although I have never known those to load by default.

I have never known these at all? Are those the visleafs or something?

Yep, they are the Visleafs, the file gets created every time you compile, and then you can load it into hammer.

Robdon wrote:
Yep, they are the Visleafs, the file gets created every time you compile, and then you can load it into hammer.

And you really should.