Thanks for your time and effort being spent here. Today I`ve solved this isse.
The bone was burried in type of jQuery function, .replace() method and RegEx.
Initially, in my playground I had this:
var $demoText = $("#gsap-anim-text-1");
$demoText.html( $demoText.html().replace(/./g, "<span>$&</span>").replace(/\s/g, " "));
So my class="article-meta" (...WP core generated php text classified by my blog theme stylesheet, and predefined in content.php) was followed by manually added variable #id ( id="gsap-anim-text-1" ). Thus my post excerpt (class="article-meta") was animated by TweenMax in an odd way with this function (with markup characters being visible, and belive me... that was not .css issue ) .
As a solution, I've changed jQuery function to :
$(this).html($(this).text().replace(/./g, "<span>$&</span>").replace(/\s/g, " "));
I think it lets RegEx /./g expression cooperate with jQuery's .replace() in a better way.
p.s. - jQuery v.1.12.2 was used in my WP 4.3.3 playground.
p.p.s. - I've left the issue in my playground untouched, for everyone to see the issue (markup being visible during animation) and try this code as a solution. Worked for me.