Stride (previously HipChat) vs IRC

You can access HipChat from pretty much every common platform. HipChat even allows chatting via SMS.

You can ping people to get their attention even if they are not online by @mentioning them. Depending on how the person has set their account up it can be by notifications via in-app sounds, visual alerts, and even email, SMS, or mobile app push notifications.

Including Asana, Github, Zendesk, WordPress, MongoDB, TeamCity, JIRA, Confluence, PowerShell and more that 40 others.

Free with unlimited users, $2/user/month for voice + video calls, screencasts, full history retention and management. (Even enterprise feature like SAML)

An intuitive, easy to overview interface listing both online and offline users.

Things like photos get automatically embedded in the chat thread once you upload them.

You can invite people to join conversations even if they don't have a HipChat account. HipChat will generate a link to share and the guest will only need to enter their name to join the conversation.

HipChat has an optional desktop client powered by Adobe AIR.

HipChat audio and video works on mobile platforms and web browsers.

Participate and keep tabs on ongoing discussions on particular topics or amongst certain groups of people.

If you are worried about third-parties getting access to your data you should consider self-hosting. With self-hosting you are in control over where your data is stored, who has access to it. You will also not be vulnerable to exploits of a third-party provider.

Pasted code can be colored based on syntax.

A big company with experience will bring in more options like Google Apps One Time Login.

E.g. part, away, all, here etc.

The IRC protocol is public and open, it is mature and stable, and has been implemented in numerous projects. This means that it can be used freely, for both open-source and commercial projects.

IRC offers choice. Choice in clients (mobile, desktop, web), in scripts those clients run, in servers and features those servers have. You can even set up your own server.

Compared to other common solutions, IRC can be ignored when you are occupied doing something else. Most clients don't pester you with sounds or distracting visuals.

Every notable IRC client supports mentions - notifying you when your name is mentioned in the chat. The mentions in IRC are comparably better than Discord. Mentions used in Discord are easily abused; this doesn't happen in IRC. If someone's talking about you, you get a notification in IRC. This doesn't happen in something like Discord.

IRC has been around since 1988, so there is a ton of existing software to work with it. Everything from clients, to chat bots, to bouncers is already built.

You can choose your favorite server for an IRC network.

No need to sign up for access, confirm your e-mail address. Just choose a nickname and you're done.

IRC is user friendly if you use something like hexchat or kiwi webchat.

Direct Client-to-Client allows users to share files in a similar way to torrenting.

Twitter hashtags came from IRC channel names.