If I reply to a message on Telegram, the original message is summarised and linked. Slack starts a weird new "thread" which hides the subsequent conversation in a difficult to access backwater.
If I want to edit a published message on Telegram, it's right there in the context menu. On Slack I have to do a complicated dance... hover over the message so that a hamburger menu appears, click on the menu, then click on the edit option. Click-drag just doesn't work.
If I want to search through message history on Telegram I click the search icon, type my search term and there are my search results. On Slack, again it's hidden behind a different hamburger menu. More click-click-click, and eventually I see my results, obscuring the current conversation! But not all of the results are there, apparently you have to pay for that.
Reactions are hidden behind a clunky hover-click-click interface.
...I could go on and on. It all kind of works, but it feels unfinished, like it's a prototype that's been bashed out in a weekend. Or it feels like a clunky web-app a-la Discord.