Also written as 靜者心多妙, this seems to be a quote from a poem by famous eighth-century Chinese poet Du Fu [0]. See in [1], where it is translated as “The serene have many marvels in the heart”. This [2] site also lists the translation “With a peaceful mind, you can create wonders”, which maybe works a bit better.
I suspect posting an arguably relevant comment in its original language was a stylistic choice more than a lapse in memory of this site’s preference for English. That said, a more complete post might indeed have included an English translation, an indicator of the source, and perhaps some other context.
[0] https://en.wikipedia.org/wiki/Du_Fu
[1] https://library.oapen.org/bitstream/handle/20.500.12657/2742...
[2] https://zhuanlan.zhihu.com/p/35880967