As there have been some critical bugs in the previous verison 1.4.2. we require the min. version for trading to be 1.5.0.
Most active traders have updated anyway already, so it should not affect many users. Also offers from users who have updated to 1.5.0 cannot be taken by users who have not updated (and the other direction as well).
The mandatory min. version for trading is broadcast as P2P network message and can be ignored if a users wish so, but that is definitely not recommended as it also contains other important data like blocked nodes (which have been retired) and banned nodes (known scammers). The option to ignore that data is mainly in place to make that feature not a risk for censorship resistence. So users who would deactive that cannot count on help from Bisq support. The program argument for deactivating would be ignoreDevMsg=true.