what does the padlock on a post mean?

ive been trying to search in help for ages.. so i thought it would be easier to ask

[humanbean]

Posts with a padlock are only viewable by members of the Thyroid UK community. Posts without a padlock are viewable by the entire internet, will appear on the NHS Choices website, and will eventually be searchable on Google.

I think (but am not sure) that posts without a padlock cannot be edited after posting.

[humanbean]

I looked at this thread a few minutes ago, and it had a couple of replies besides mine - one from Nikki365 and one from Clutter. I tried replying to Clutter, submitted my reply, but it failed to submit with "This is embarrassing, this post doesn't appear to exist" or words to that effect. And now the two replies other than mine have gone.

My second reply to Clutter was acknowledging her comment that ALL posts can be edited, not just the ones with a padlock.

[Hidden in reply to humanbean]

I've noticed my end both mine and clutters replies have disappeared....

[humanbean in reply to Hidden]

The gremlins are attacking again. HU has rather a lot of them.

[Hidden in reply to humanbean]

Probably endos gremlins