ELO is a chess statistic which assumes equal weight across all matches (no surface weighting, and no tournament weighting - a 250 is viewed the same as a Slam) and for this reason has very little place in the context of informed tennis discussion.
I don't think this is fair. The problem is not that Elo (it's Elo, not ELO by the way) has little place in informed tennis discussion but that people are not sufficiently informed on how Elo works leading to confusion and frustration on how it rates different players from history and present.
Some people appear to think intuitively that Elo peak should be representative of the highest level they ever saw a player perform at. But it would in reality be practically impossible to create a mathematical formula to express such a thing.
You could, however, calculate individual tournament Elo performances, and that would actually spit out a number representative of the incredible feat that someone like Wawrinka pulled off at the Slams he managed to win.
But standard Elo itself is not really a "peak level" number. It's more of a "number representing the level of match-winning consistency this player is performing at".
In other words, it favours players who go deep in tournaments consistently over players who sometimes win a tournament and other times crash out in the first week. When you think about how exactly it works (it's not that complicated!), this all makes sense and you can use Elo appropriately in "informed tennis discussion".
Just don't try to use it to try to claim something it's not capable of measuring; like that peak Ferrer would've beaten peak Safin or Wawrinka at their Slam winning tournaments or something weird like that.
