Since updating to XF 2.2.7 when using 2 emoji's in a row the second one will start a new line. Using Windows 10 and Firefox 92.0. Checked here and confirmed it happens.
The fr-marker bits are being removed after inserting instead of when the dialog closes, this results in the 2nd smilie being added after the <br> at the end of the line when a smilie is inserted into a blank line.
Sorry it appears to have not been resolved in 97.0.1. I'm running macOS. Same issue, not able to add a few smiles in a row, after adding the first smilie a new line starts.
Very strange, it was correctly right after I did the Firefox update but just checked again the problem is still there. Firefox 97.0.1 and latest version of Windows 10 Home and Pro here.