Right or Wrong

17/2 + 7 = 15.5. (applying the "Half-your-age-plus-seven" rule - https://en.wikipedia.org/wiki/Age_disparity_in_sexual_relationships)

So if it's more than 6 months since she turned 15, then pursue. But as you note, remember the legalities.

Not with a ten foot pole

That 'rule' is about an observed pattern in existing relationships. It is not a guideline for what is acceptable, either socially or legally.

Just looked it up, seems he might have some wriggle room on the RoSO but still serious risks

prosecution and jail is possible

The Act does not apply in cases of defilement of a child aged under 17 years if:

• The victim is aged between 15 and 17 years of age when the offence takes place, and
• The person guilty of the offence is less than 3 years older than the victim

deals with defilement which appears to not be called rape if victim under 18

https://www.breakingnews.ie/ireland/teenager-gets-one-year-detention-for-defilement-of-girl-after-breaching-conditions-1441991.html

If youth workers are going around spouting that nonsense there we might as well write the next generation off completely.

But they're not, are they? Because you made that bit up.

(And if you had read the article to which you linked you would have noticed that it is assumed that both parties are 14 years older than the age difference, so it can't apply here.)