Teams Change notifications subscription with search query parameter in message collection succeeds but webhook not called when multiple special characters are used ex: ??!$%^*()_-{}:;,.<>/

[ReniKIcon17]

Here it mentions a simple word usage of pizza as a search parameter, but doesn't offer much guidance on special characters that can be used. Similar doc here for Teams change notification subscription.

I imagine you have to escape the search keyword when multiple special characters are used and such an escaped search string succeeds in creating a subscription, but the webhook doesn't get called when the same keyword is used in the message.
Any ideas on the recommended usage of special characters in search parameter if this is not a bug?