We classify the “fully tight” simply laced Coxeter groups, that is, the ones whoseiji-avoiding Kazhdan–Lusztig basis elements are monomials in the generatorsBsi. We then investigate the basis of the Temperley–Lieb algebra arising from the Kazhdan–Lusztig basis of the associated Hecke algebra, and prove that the basis coincides with the usual (monomial) basis.