We performed follow-up measurements of this object while it was still on the PCCP webpage.
Stacking of 5 unfiltered exposures, 90 seconds each, obtained remotely on 2021, February 22.2 from X02 (Telescope Live, Chile) through a 0.6-m f/6.5 astrograph + CCD, shows that this object is a comet with a compact coma about 8" arcsecond in diameter. (Observers E. Guido, M. Rocchetto, E. Bryssinck, M. Fulle, G. Milani, C. Nassef, G. Savini, A. Valvasori).
Our confirmation image on top (click on it for a bigger version; made with TYCHO software by D. Parrott).
M.P.E.C. 2021-D113, assigns the following preliminary parabolic orbital elements to comet C/2021 C4 (ATLAS): T 2021 Jan. 21.04; e= 1.00; Peri. = 320.80; q = 4.50; Incl.= 132.85
by Ernesto Guido