The only thing comments could do in compiled languages like C++/C# is increase the compile time by very small amounts as it parses through all of the files (you would needs thousands and thousands of comments to actually notice this). The execution speed at runtime isn't effected.
If you are using something like HTML it is a slightly different story as all of that data still has to be transferred around networks, but otherwise don't worry about it.
Commenting excessively is clearly a bad idea though. It's going to make the code harder to read and understand - The opposite of what comments should be doing!