Double Posts
I personally think the "no double posts" rule is a good one in most cases. There's a limit to the number of posts on each page, and it would really irritate me to have an entire page of one-sentence statements all by the same poster. Plus, it's basically spam at that level.

OTOH, if you're responding at length to two seperate things in the same post (ie. at least a full paragraph for each) seperating into two posts isn't as much of an issue, and makes sense, since people often skim lengthy posts. Alternatively, you can insert a line break and slap a bold title when you change topics (sorta like you did for your questions).

In case anyone else is wondering, for line breaks:
Code:
[hr]
[hr]
Monthly Comic Thread vs Comic Specific Threads
Anyways, Zherog's historical review covers things nicely on that front, but I want to add a bit on the logistical side. For one, there are already over 200 comics - if each has it's own thread, that's 200+ threads in comics alone, with the number constantly growing. And I have no doubt that threads for older comics would be needed, since Rich has new readers all the time. That's a lot of threads. If they're user created, you'll likely see numerous instances of duplicate threads, which a mod then has to deal with. If they're mod created... well, that means an intial startup of 227 threads as of right now. Ouch.

Additionally, since the OotS comics are part of a continuity, rather than each standing fully alone, you can't really discuss a single comic all by itself - the connections to older ones often get brought up. The fact that discussion comes up in a continious thread makes this a little easier to follow. The reason it's biweekly or monthly (the thread gets renewed about once every 2-4 weeks, depending) is to avoid the horrendous load times Zherog mentioned - the time cap is simply a nice, easy way to deal with it. The other option is to decide on a number of pages to cap the thread at, but that can be a bit harder to wrangle.

Anyways, just my 2cp.