We've found this problem in this question on Stack Overflow in Portuguese, but I've also tested in other sites (English and Spanish SO's), and it happened there as well.
In the aforementioned question, there's a code block, with the following markdown:
```text
----------------------------------------
FILHO 1
----------------------------------------
FILHO 2 | FILHO 7 | FILHO 12
FILHO 3 | FILHO 8 | FILHO 13
FILHO 4 | FILHO 9 | FILHO 14
FILHO 5 | FILHO 10 | FILHO 15
FILHO 6 | FILHO 11 | FILHO 16
----------------------------------------
```
But the page is being rendered as:
Please note that some parts of the code are bold: the line FILHO1 and the line starting with FILHO 6 (and the lines with hyphens that come right after them).
It happens on both questions and answers, and it's happening also in the preview, but not all the time.
Doing some tests, I could reproduce the problem only when there are at least two language tags in the question, as the gif below shows (that's the preview in Ask a Question page, on SOpt, the markdown is exactly the same as above):
The presence of two language tags seems to be what causes the problem. When there are other non-language tags, they don't seem to affect the rendering.
Note: I also suspect that it might be related to the language hint (in the block above, it's text, which I believe it's an invalid one). If I don't use any language hint, the problem also happens, but if I use a valid language hint (such as ```java, then the problem doesn't happen).
This gif was made on SOpt, in the Ask a Question page. But it also happens if I'm answering a question with at least two language tags (tested on SOpt, SOen and SOes - I've checked only the preview, because I didn't want to pollute the sites with "test-answers"). I also couldn't find other questions with these specific characteristics (two language tags and a similar code block), but I'd appreciate any help finding those.
