From that thread it's clear that the ZNC devs have bought the IRCv3 ideas hook line and sinker and have no regard for the effect of ZNC's adoption of those ideas on IRC clients. It is not up to mIRC to avoid that the ZNC devs alienate their own userbase. Moreover, suggesting that a timestamping problem be fixed with echo-message is akin to trying to kill ants with a sledgehammer: it won't be fully effective(*), and you're going to cause a whole lot of damage in the process of trying.
I'm pretty sure it's possible to write a script that implements the necessary level of batch support already, but ultimately, this is ZNC trying to impose its own world view for no good reason, and it is important to realize that that is the core of the problem at hand. If anything, the takeaway is that mIRC should stop interpreting server timestamps, and instead leave it to scripts to do so if they choose. A step back in terms of "IRCv3", but if mIRC cannot rely on the other side behaving sanely, it has little choice.
(*) In summary: mIRC also has local output that may be timestamped, for example from local commands. This very simple fact breaks the fundamental server-time assumption that all timestamps come from the server. As such, the entire discussion about keeping clocks synced fully misses the point.
