@lynnesbian Oh hey! I'm the person who originally submitted this to reddit.
As far as I know, this rule is no longer in place. It still shows up in some recent-ish documents (like ), but a train driver I know showed me a screenshot of a document explicitly stating that this paragraph was made obsolete.
It also doesn't show up in the current R 300.5 anymore. 
@lynnesbian I think the original limitation was caused by mechanical counters with eight physical bits (so, not actually software), which have now been phased out.
@lynnesbian Whoops, link  was supposed to be this: http://eisenbahnberatung.ch/Dokumente_Web/R%20I-30111.pdf
@draemmli thanks for clearing this up! i managed to find a slightly more recent document mentioning it, but you're right, it seems to have disappeared now
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