In IRV, cases of clear opportunity for strategic voting are not at all rare, nor are they hard to detect. All you need is to see that a compromise candidate is in third place by lead preference, and that your wing candidate would probably lose in the runoff. This is hardly inaccessible information, requiring only one horse-race poll and the most obvious head-to-head poll.

What you face is a flat cost in terms of settling for a non-first-choice, in return for bolstering your chances of avoiding a strongly non-preferred outcome. It's a chicken strategy, rather than the berserker strategy that's your only opportunity with Condorcet.

In effect it pulls IRV back towards FPTP in terms of voting behavior. Not all the way, to be sure - you're perfectly safe putting the extremely silly party on the top of your ticket, and if there are more than three major parties, each with a credible chance at winning, it gets to be sufficiently difficult to project consequences that the benefits of defensive strategy are no longer clear.