1. Certain synagogues do not permit the sheli’ah tzibbur to repeat words, phrases or pesuqim in the prayers. 2. Some hazzanim frequently repeat such words, phrases and pesuqim. 3. Is there any poseq who permits this? If so, please give references.
Rav Ovadya Yosef (Yabia Omer 6 OC 7 4-5) collects all of the major opinions on this topic. The conclusion is clear that this is a bad practice, and one who has the power to stop it, should do so. (See also Responsa Sheilat Shelomo 1, 24; and 7, 32) Those Chazanim who repeat words only in order to enhance the Kavanah of Tfilah, have a minority lenient opinion to rely on (Responsa Ziknei Yehuda 131) though; it is highly discouraged, to say the least.