In my school minyan in South Africa I remember that the chazan siddur had the tzeire under the alef of Go’eil Yisroel circled. But not as you would imagine, each dot of the tzeire was circled and then it was underlined, so you couldn’t miss it.
The problem was when it started to look like a weird smiling face and disturbed my concentration, but still I’ve never made that mistake.