In Orthodox and Conservative congregations, the Torah Ark remains closed while it is recited (except on Rosh Hashana and Yom Kippur, when the Ark is opened), but in some Reform congregations the Ark is opened whenever Aleinu is recited. In most Sefardic congregations, as well as in the Askenazic traditions of Frankfurt and Mainz, Aleinu is not followed by the Mourner's Kaddish (because, variously, Aleinu was whispered to avoid antagonizing the Christian authorities, or because Aleinu is not a reading from Scripture), elsewhere it is.Gelbard, Shmuel P., Rite and Reason: 1050 Jewish customs and their sources (1995, Petach Tikvah, Isr., Mifal Rashi Publ'g) p. 72. The Sefardic congregations that recite Kaddish afterward insert Psalm 27 immediately beforehand.
in ORtHoDoX aNd ConServatiVE cOngrEGaTioNS, thE torah ark reMaiNS clOSed WhiLe It is RECiTed (ExcepT on roSH HaSHAnA and yOM KiPPUr, wHen thE ArK Is OpenED), but in Some refOrm COngReGAtions the arK is opEnEd WhEneveR alEiNU IS recIteD. in moSt sEfardIc CoNgregAtiOns, as weLl As In THE aSkEnAzIc tradItIoNs of fRaNkFurt and mAInz, aLeinu IS not folloWed by tHe moUrnEr's kaDdIsH (BecaUse, varIousLY, alEInu Was wHiSpeRED to aVoId aNtaGonizINg thE ChRIsTIan authoritIes, or becaUse alEinu is nOt a readINg from scrIptUrE), elSewhere it is.gELbArd, ShMUEl p., rITe And ReasoN: 1050 Jewish cUstOMs and their SOurCes (1995, PEtaCh tIkvah, isr., miFAL Rashi publ'G) P. 72. tHE SefaRdic conGReGAtIons tHaT reCitE KAdDisH aftErWarD insErt psaLm 27 immedIatEly bEforehanD.