Usage of drop caps in terms of UX

Short question
What is the benefit of using a drop cap for the user, beside the decorative element? I really dislike them, but I don't have proof and only my opinion to discuss with.


What is a drop cap
enter image description here
The drop cap, also called Initiale, is the first letter of a paragraph in order to draw attention to the block and use it simply as a decorative element.

What I don't like about it
I just read a blog entry by InVision. The blog entry startet with a drop cap.
enter image description here
So I started to read "s designers, ...", stopped, and started to read again because I simply ignored the drop cap and was confused about the begin of the sentence. And it's the start of the whole article. Why do you need to draw extra attention to the first paragraph?
And if it would be in the middle of a article, it would simply interrupt my reading flow.

Second thing I dislike about those is the problem about marking the text. Let's take the same article again as an example. I just want to mark the first few word.
Naturally, I set the cursor in the middle of the first letter of the sentence I want to mark.
enter image description here
The result is, that I automatically mark also the sentence below. And visually, the marking background doesn't look very good.
So I try to mark the letter at the top in order to mark the first few words:
enter image description here
The first result was, that I didn't copy the drop cap. Only in my second attempt I was able to mark the drop cap as well.

What I found about the UX of Drop Caps
Most of the articles only talk about, how to achieve this effect or how long it's been around. The only article I found, talking briefly about UX was an article by Smashing Magazine: Drop Caps: Historical Use And Current Best Practices With CSS. It says:

Illustrated caps increased usability by marking important passages and guiding readers through the text.

Simply not. Yes it marks important passages, bug it interrupts my reading and don't guide it!
In the next sentence, it just reverts what it just said

(...) drop caps on the Web don’t add value in terms of usability or readability (...)

Why I need proof for it
Our visual designer want to add those drop cap's in our company blog and I (only UX Designer in the company) strongly disagree with him, without having real proof.