How would you translate "He is somewhat tall?"
挺 /tǐng/ = quite; rather
If a man is 170 cm tall, he is of above-average height for a Chinese male (164.8 cm), and we can describe him as 挺高. But it is not that rare. On the other hand, a Chinese male over 190 cm tall has to be considered 很高
We only describe 姚明 as 很高 (very tall), never 挺高 (quite tall), I mean, he is really tall.
More example:
85% mark is 挺高分數 (quite a high mark - high but not rare); 95% is 很高分數 (a very high mark)

How would you translate “He is somewhat tall?”

他人挺高的 (he is quite tall)