Yes, the atstrings feature is turned off by default in Arc 3.1 (and also in Anarki's official/stable branches). I think I'll turn off the default in Anarki as well, and just let news.arc continue to make use of it.
Edit 1 hour later: This is now done. Turns out Anarki never meant to turn on atstrings by default. This was a side effect of loading news.arc by default (mea culpa). I've changed things so we load news.arc by default but only use atstrings in news.arc by default. Keep an eye out for subtle bugs introduced by atstrings being turned off when functions in news.arc are called. If we see any I'll probably take out the ability to turn it on and off and just decide to keep it everywhere or take it out entirely.