Query string causes problems

Thanks for acknowledging the issue. I am tempted to say that the particular service (Kayako help desk software) where this problem appears should fix their "problem" that is, their sensitivity to a query string parameter that they don't care about. It looks like Kayako has a bug - more evident in the pic below - because 1P's parameter is a named parameter but in the diagnostic, Kayako has squeezed out the equal sign, so now the query string looks like a giant unnamed parameter and I can understand sensitivity to unnamed parameters (as compared to named parameters).

In other words, your team is doing a reasonable thing by using a named parameter. Kayako is doing the wrong thing by misinterpreting it as an unnamed parameter. That said, I would still suggest 1P use a parameter name that starts with "1Password" to avoid inadvertent clashes. You can't blindly share namespaces.

I can imagine you're reluctant to contact services that cause problems for 1P but in this case, Kayako appears to be a popular provider and might well be interested in hearing a bug report from you. (I'd report it myself but a report from 1P will have more oomph.)