This is a very basic requirement that HubSpot again does not deliver one. A global business has people of names that do not fit into the US ASCII 128 charset. Any URL should be encode for this.
Our issue is with {{contact.firstname}} and similar replacements in form parameters. When you have a first name like e.g. ‘Hans Henrik’ then all links crash and gives a 404.
We need to have all chars encoded and/or replaced as suggested here.