https://www.limesurvey.org/de/foren/can-i-do-this-with-limesurvey/121097-update-response-by-token

In this thread it is discussed on how to pass a parameter from the token table to the survey in an anonymized token-based survey. Of course this would mean the survey can not be guaranteed to be 100% anonymous in a "technical" sense. The user found a solution to pass on the parameter via URL. In the specific case is is said to be something rather not so critical (the group of a respondent), but you could pass on any parameter, even specific IDs, Names, emails, etc.

However, this means that LS states that the survey is "technically" anonymous, but it not really is, if in an anonymized survey parameters can be received.

I think for the "anonymous" surveys setting in LS we should not allow parameters in the URL, because it could backfire to Limesurvey. Of course we can always say "Ohhh, this was the survey creator who did this", but when it is so simple to get around the "anonymous" measure, I think it doesn't shed a good light on Limesurvey. So I think we should make it as difficult as possible to maliciously get around the "anonymity" of a survey set to be "anonymous".

I don't see a problem with normal surveys. No one can blame LS then, if the survey creator states it is anonymous, but it isn't. But with the setting within LS, it is basically a statement of LS and if we accept URL parameters besides the LS ones, we can't really guarantee it.