So, there is considerable evidence in favour of drawing a categorial distinction between the preposition for and the complementiser for: they are different lexical items (i.e. words) belonging to different categories.

As young men will, I did my best to appear suave and sophisticated.

It started with that fateful trip, history was never the same afterwards.

Gradually, the salty smell abated, or perhaps they had just become nose-blind to it.