The phrase "harps upon" is commonly used to describe someone who continually emphasizes or repeats a point in conversation. However, there are other synonyms that can be used to avoid repetition in writing and speaking. Some similar phrases include "hammering home," "reiterating," "fixating on," and "dwelling on." "Emphasizing," "highlighting," and "underscoring" are also good alternatives. For those specifically looking for synonyms with negative connotations, "belaboring," "laboring," and "overemphasizing" could be used. Overall, using varied and appropriate synonyms can make communication more effective and engaging for the listener or reader.