monaco-editor npm version: 0.7.3
Browser: chrome/ safari
OS: OS X
We experience some odd styling differences for signature help between safari and chrome.
Safari:

Chrome:

try here : http://52.29.251.2/calcmonaco/
The following CSS seems to fix your issue:
.monaco-editor .parameter-hints-widget {
flex-direction: row !important;
}
This bug only occurs if there are not multiple overloads, from what I can tell.
@svenefftinge Was this caused by some CSS collision on your page or is this something that fails with the editor out of the box?
This fails out of the box on Safari. Try this in the Monaco playground:
function abc(){};
// function abc(x){};
abc();
Uncomment the second abc overload and everything works fine.

https://microsoft.github.io/monaco-editor/ Seems to work well in safari
Yes, seems fixed (either via Monaco or via Safari 12).
Most helpful comment
The following CSS seems to fix your issue:
.monaco-editor .parameter-hints-widget {
flex-direction: row !important;
}