Re. incoherence of vim's keybindings, I partially agree.

Most of the times, shift means "bigger", and only in a few places it means "invert".

Examples of "bigger" are all the motions involving words vs. WORDS, where WORDS are a broader interpretation of words; "V" is like "v" but by lines, thus in larger chunks; "C", "D", "Y" do the same as their unshifted counterparts, but extended to the end of line; etc.

Examples of shift meaning "invert" are fewer, and all sound irrational to me:

With x/X and o/O, the shift inverts the direction left/right or above/below, but we don't have for example i/I to insert to the left/right of the cursor, and H is not the opposite of h, J is not the opposite of j, etc.

With n/N, shift inverts next and previous. Why not n/p? I know, I know: p was already taken for paste, but still...

Finally, t/T/f/F are completely mixed up. In my mental model, t/f sound like to/from and I'd rather use them to move forward/backward till (not including) a char, while T/F would be the "bigger" variants which include the destination char.