This was patched in last week. It was mentioned in the patch notes but doesn't seem to have gotten a lot of attention. I thought this was a nice QOL addition. A big thank you to Daybreak.
There was quite a long thread on this a few months ago, and the general consensus I think was that it would be nice to have. A good example of the Devs responding to something positive. I use tell windows, so if I have to go afk for a while, it's nice to see when a tell was sent (or when one tell gets hidden behind another). I'll have to try this new feature out, see how it works.
Oh, and thank you for reminding me. I like this cause then I know when what was offered in chat and don't chime in 45 minutes later lookin like a foo.