Ctrl-i and ctrl-b can be used in reblogs for italics and bolds
You can post reaction pics by first rebloging to drafts, then editing the draft with the rich text editor.
Tags on reblogs don't make the post show up in the search, but they will make the post show up when browsing by tags.
There is no limit on indexed tags, unlike tumblr where only the first ten were indexed. (But don't spam the tags with irrelevant tags; you will get reported. I will report you.)
There is no option to tag "ask" responses when answering an "ask". However, you can tag it once posted by editing the post, and then you can easily find asks by searching your blog.
The queue hours don't wrap. If you set the queue to 13 through 1 (for 1 pm to 1 am), it will disable the queue. Instead set your queue to 11 through 23, then use a time zone two hours earlier.
Blog settings, such as the queue parameters or online status, are not shared between the primary and the side blogs.
Staff is super-friendly and helpful. Every bug report I've submitted has had a real person respond with 24 hours -- usually within 2 hours -- even when it's 2 am in the States. The feature requests on the zendesk boards also get attention, and a lot of the more recent features have come directly from there.