For large numbers, you might get a stack overflow. Depends on whether the compiler recognizes that it's a tail recursion and then handles it appropriately.
As for why Lemmy ignores single newlines, that's because it uses Markdown for its comment syntax, which happens to handle newlines that way. If you want a single newline to display, you have to add two spaces at the end of the line.
Here, you really would have wanted to use a code block, though, which you can create with backticks
```
like
so.
```
Normally, this would display "like so." in a monospace font and handle newlines as you expected:
like
so.