May dashes be used in place of commas or parentheses?

Yes. When used this way, dashes are significantly more emphatic than commas and slightly more emphatic than parentheses:

Always remember that at any one point in time‚‚especially

when under stress‚‚one style will predominate.

In like manner, dashes may be used to insert a thought within a sentence that is related to but not directly part of the main idea of the sentence:

Our committee was given the responsibility for developing

goals and objectives‚‚a mission statement had been created

by an earlier task force‚‚that would be implemented by all

departments involved in the quality improvement program.