(They added the third f or maybe re-added it)
(They added the third f or maybe re-added it)
https://de.wikipedia.org/wiki/Reform_der_deutschen_Rechtschr...
... several times: 1996,2004,2006,2011,2017.
The current correct spelling is either Schiff-Fahrt or Schifffahrt.
Once upon a time we used to write by hand. It was considered time consuming.
Once upon a time we used to set books in lead letters. There were ligatures, where two consecutive letters hat a special spacing - like "fi" or "sz". If we allowed three consecutive letters, we would need to invent new ligatures.
It is probably easier/cheaper to just forbid the spelling.
Also, there are portmanteau words where the middle letters overlap, e.g. bro+romance=bromance.
https://www.etymonline.com/word/chaffinch
There may be others.
When we turn to the letter 'l', we have the word skill-less which is not always written with a hyphen, in which case the three l's remain intact.