Not sure if you know.
Everything you do on hive costs "Resource Credits" or "RC" for short.
RC will generate back overtime, but it requires Hive Power or borrowed Hive Power powered up in order to generate faster.
This is really just an issue in the start, but it also means that when you earn a bit of HIve Power/HP, you will be able to post and comments more, even vote on other peoples posts ^^
You also have 0.023 hive in your wallet which you can power up to help you get more RC :D