JSFiddle - React, Tailwind, and code Playground

HTML

<div>Diskuze obsahuje <span class="comment" data-count="1" data-plural-1="komentář" data-plural-2="komentáře" data-plural-3="komentářů"></span></div>

<div>Diskuze obsahuje <span class="comment" data-count="2" data-plural-1="komentář" data-plural-2="komentáře" data-plural-3="komentářů"></span></div>

<div>Diskuze obsahuje <span class="comment" data-count="5" data-plural-1="komentář" data-plural-2="komentáře" data-plural-3="komentářů"></span></div>

CSS

span[data-count]:before{
    content: attr(data-count)  ' ';
}
span:after {
   content: attr(data-plural-3);
}
span[data-count='1']:after {
    content: attr(data-plural-1);
}
span[data-count='2']:after, span[data-count='3']:after, span[data-count='4']:after {
    content: attr(data-plural-2);
}