I often see people write stuff like
$cos(\theta)$, were I'd like to a
\. The system does not let me make such a tiny edit.
Is it so that the peer review queue is not filled with so many edits?
On the larger sites, i.e. the original trilogy, then yes, that is probably the reason. On this site, it doesn't matter so much, but all the sites use the same code, and I don't think the team considers this important enough to allow one-letter edits here. In any case, there should always be something else you can edit at the same time.