Update the Member Handbook to include a note about rich previews

Author: ivanreese

episodes/049.md

@@ -1,9 +1,9 @@
+[These are Ivan's working notes as he edits the episode — please ignore for now]
+
 Back in the previous life, I sent a link to slides that present an overview of several ideas behind Sketch-n-Sketch. In case you think it would be useful as a link, here is something similar but in text form (this "research statement" is part of a tenure review file that I just submitted):
 
 http://people.cs.uchicago.edu/~rchugh/static/other/chugh-research-jun-2020.pdf
 
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 I forget whether we talked about plans to teach a new Creative Coding class, but now it's official and slated to start next spring. Not that I think linking to this course catalog is interesting, but it includes the course description in case you find that useful. I'm happy that Creative Coding will count towards a recently-created Media Arts and Design minor. I haven't written anything for this class yet, but I did have fun posting this:
 
 https://twitter.com/ravi_chugh/status/1229751960737394690

member-handbook.md

@@ -23,6 +23,8 @@ When you want to respond to someone's post, always use threaded replies. On desk
 
 Please try to keep thread replies on-topic with respect to the original post. If you want to fork a discussion off in a new direction — say, if you feel a tangent coming on — by all means start a new top-level post that includes a link back to whatever message sparked your digression.
 
+When you post a message that includes links, those links will often generate rich previews that appear under your message. If you link to a video, the preview will allow the video to be watched right from the Slack. This is nice! But often, these previews don't add anything of substance, and they eat up a lot of scroll height. In this case, please delete these rich previews (which, AFAIK, can only be done using the Slack web or desktop clients, not the mobile app). Note that community moderators may remove these previews too if they aren't adding much value.
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