Messages written on walls are usually preserved only when somebody photographs or writes about them , thus transferring them to a flimsier but more enduring medium .

墙上的涂鸦经常被一些人拍下或是把它们写进文章里而得以保留，这样就被转变到一个更加脆弱但更持久的介质。

This sounds like an advantage , but it may imply just the opposite : that police arrest asians on flimsier grounds than they do others .

这听起来是个优势，但也可能正相反：比起其他种族的人来说，警察更加没有立场逮捕亚洲人。