I'm sure that this is not a coincidence, that it was very well thought out by the designers of this app, but I can't seem to understand why. In the timeline, they use a sans-serif font, while in the main tweet view, they use a serif font. What are the reasons for this?
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I think that it has multiple purposes.
1) The font on the main tweet view is a little bit smaller so harder to read when you would use a serif font (not to mention hideous)
2) It makes the user know that he/she is on the tweet page or on the personal page just by swiftly looking at the screen. It's used as an eyecatcher and gives some visual differentiation.
Atleast that's what I think
I have always found serif fonts more appropriate for small length texts such as quotes. The maximal length of a tweet is 140 characters and to me serif fonts seem more appropriate.
The tweets featured in the menu are smaller size and undoubtedly look better in sans-serif fonts so it is logical that they are written in Helvetica.
