The media section is essentially an in character free for all. You may post whatever you like in them (except the news, which is only admin post-able, and will be used for plot updates), and you may format them however. In Travis' first vlog, I made it much like a regular post that was dialogue-heavy. If you'd like, you can comment back in a similar fashion, or even post something like this:

ACCOUNT NAME:
lol ur video sucks.

Remember, diaries are off-limits in character for others to read unless the RPer makes it a tangible thing that they ALLOW YOU to take and read. Vlogs, blogs, etc., however, are all fair game and you can read, comment, and bash the makers as much as you'd like.