Delete DialogUser in old HistoryDBs

We are running now 9.2 and we have a HistoryDB just for that version.

We also have a peer HistoryDB for old Version, which are not migrated to newer Versions.

Means that we have Archive_V82, Archive_V8, Archive_V7, ...

Now I want to get rid of any SystemUsers that are not needed anymore but could trigger a security audit finding.

As far as I understand, there is no need at all to keep the DialogUser entrys in the old HistoryDBs?
So I can just delete them, or at least flag them as isLockedOut.

Is there any concern for that approach?