#4 has introduced an interesting problem in the MMO space. By allowing scripting in WoW, players were penalized either because they couldn't keep up, or the general community would demand they run parsers to tell that they couldn't keep up. The vanilla experience was no longer good enough. FFXIV decided to ban any client customization in an attempt to avoid these kinds of toxic situations:

https://www.reddit.com/r/ffxiv/comments/5uxmx8/yoships_offic...