Group: Performance

There are a few rea­sons:

1. If I processed at the time of sav­ing a post, the changes are de­struc­tive. This means: 
   • If peo­ple to back to ed­it their work, there will be a mul­ti­tude of hid­den char­ac­ters that will in­ter­fere with their ef­forts
   • Spell check would be bro­ken (in browsers like Fire­fox)
   • If you dis­able the plu­g­in, the changes are still hard­cod­ed, and will not go away.
2. Changes would on­ly ap­ply to posts saved af­ter the plu­g­in was en­abled (not on pre­vi­ous posts, since they have al­ready been saved, and thus would not trig­ger the ty­po­graph­ic fil­ter­ing).
3. Set­tings would not be editable-​since pre­vi­ous fil­ter­ing is stored in the data­base, if you turned off hy­phen­ation, that would on­ly ap­ply to new posts saved.
4. For most in­stal­la­tions, caching re­solves per­for­mance is­sues.

But to be hon­est, the biggest rea­son is if there is a bug in my code, I don’t want to be re­spon­si­ble for de­stroy­ing da­ta in the thou­sands of web­sites that use this plu­g­in. If some­thing goes wrong, they can just turn it off-​no dam­age done.

Yes. Use WP Su­per Cache.