The text uses combining characters, also known as combining marks. See section 2.11 of Combining Characters in the Unicode Standard (PDF).
In Unicode, character rendering does not use a simple character cell model where each glyph fits into a box with given height. Combining marks may be rendered above, below, or inside a base character
So you can easily construct a character sequence, consisting of a base character and “combining above” marks, of any length, to reach any desired visual height, assuming that the rendering software conforms to the Unicode rendering model. Such a sequence has no meaning of course, and even a monkey could produce it (e.g., given a keyboard with suitable driver).
And you can mix “combining above” and “combining below” marks.
The sample text in the question starts with:
- LATIN CAPITAL LETTER H –
H - COMBINING LATIN SMALL LETTER T –
ͭ - COMBINING GREEK KORONIS –
̓ - COMBINING COMMA ABOVE –
̓ - COMBINING DOT ABOVE –
̇