Omit the H (h(エッチ)抜き, ecchi nuki) is the internet etiquette rule of removing the 'h' from 'http://' or 'https://' to avoid how most modern websites would automatically convert URLs into hyperlinks. It's a bit of a dying art, especially when most 2channel users have moved to Twitter.

The reason behind omitting the 'h' is to deter search engine indexing and ensure that the website's owner does not see the referer, as there used to be a culture of forbidding 'unauthorized' links or it could be used to discuss things (e.g. slander, piracy, etc.) without tipping off their owner. It was also the workaround if a board decided to blacklist or forbid posting links to deter bots that spam a wall of hyperlinks.¹⁾

On the other hand, this way of linking is seen as an 'inconvenience', has lost its meaning over time, and a developer could either code in a 'fix' to force a hyperlink, ruining the point, or have these links be truncated which makes it more difficult to extract the correct link from the post.²⁾ In addition, referral hiding services, like href.li or anonym.to, are much more convenient.

• There's also the possibility that this was done to avoid interstitial webpages (e.g. jump.2ch.net) since these typically had advertisements whose revenue would go to the website owner.

• Omit the H on Niconico Encyclopedia
• Omit the H on Japanese Wikipedia