I use the Ubuntu font for all programming activities.
In OSX, if these characters are in some line, the line height will grow to make room for them. Thus, different lines will have different heights, which looks strange (see attached screenshot left side). Even entering these characters in the textbox on this very website made the line height grow beyond the bounds of the textbox.
In Windows, the characters are shrunk to fit the line height. However, this shrinks different characters to different degrees, so the triangles end up having different sizes. (see attached screenshot right side)
Most prominently, these characters are used in the popular TagBar plugin for Vim as disclosure triangles.
The left side of the attached screen shot shows a section of a MacVim buffer with the characters in question. You can see how the characters distort the line heights. The right side shows a Visual Studio buffer where you can see how the characters are shrunk to different degrees.
I am also experiencing this with the arrow characters (←, ↓, ↑ and →). They take too much place in Ubuntu Mono, both vertically and horizontally, making lines expand and also distorting the rest of the line where they are inserted.