Hi rorym, please separate between key and value (key=value). For keys I cannot find any special symbol-sign. Only for some values. And keys are more problematic, see also taginfo for this.
Thanks, Alex

Firefox under Ubuntu) can show the symbol fine, but Google-Chrome under Windows-7 does only show rectangles.
try 2 OSM links (examples),
www.openstreetmap.org/way/633453943
taginfo.openstreetmap.org/keys/%F0%9F%8F%B3%EF%B8%8F%E2%80%8D%F0%9F%8C%88

I have seen many issues last years with problem-keys or problem-values. E.g. the char 0x7F (a char that is meant to be ignored, to delete what was there, needed in historic times) is interpreted different in OSM tools: some ignore it (as intended), some handle it as an invisinle char without size, some as a space. It caused names including it to be not searchable, even if it was the first or last symbol of string.
keys are more problematic tha values, as no all DB-server-engines out there can handle it as a valid column-identifier.

please revert this change, because it is problematic for many tools.
there is a good reason why you can find it here:
https://taginfo.openstreetmap.org/reports/characters_in_keys#problem

I think OSM is a database, no funny looking text book. Your tag is the only emoji-key in the whole database!

Many thanks, Alex

Hi Anthony Schoenduby, please follow the OSM wiki and put ele-tag always in meters.
osm.wiki/Key:ele
If you need it in feet, you can add "ele:ft" tag.
As OSM is an international project the database follows international standards.
Thanks, Alex

Hi, please only add wikipedia-tags that exist !
"https://ro.wikipedia.org/wiki/DJ144" is not there.
Thanks, Alex

Hi Dartmouthmapmaker, please follow he OSM wiki and write wikipedia="lang:Article" (using language code like "en:"), see osm.wiki/Key:wikipedia
Thanks, Alex

Hi km2bp, please follow the OSM wiki, wikipedia="lang:Article" not "http..".
osm.wiki/Key:wikipedia
Thanks, Alex

Hi Nomadmapper,please follow OSM wiki,
osm.wiki/FR:Key:wikipedia
ikipedia=fr:Gare.. not ="https.."
Thanks, Alex

hi Kirill Nemov, please do not enter empty tags!
If you do not know the name of this school, please write fixme=name.
Thanks, Alex

Hi NaKlarNaKlar, bitte folge dem OSM wiki und schreibe wikipedia=de:Artikel (mit Sprachkürzel).
osm.wiki/DE:Key:wikipedia
Danke, Alex

hi Armando, what means your tag @=yes in way/636971963 ?
regards, Alex

Hello Woodpeek. I'm sorry. Is there a way to tell someone that there is something big to repair (except adding a comment or a fixme-tag)? Can I revertmy change by myself? Could some auto-revert for adding impossible tags (like empty key or value) be introduced on server side? I sometimes feel, that OSM needs some automatic warning system (as auto repair) is not liked too. Could I in future inform you, and you try to confirm or answer within some reasonable time? I really tried to help and again it was not compliant. I will stop big-edits, without getting confirmation by you - if you want. I hope we can find a way of overall hapiness.
many regards, Alex

Hi onloma, you have added empty tags to about 200 nodes in CH (Schweiz). This was not there 2 days ago and it is only localy (CH). Please be careful when changing tags and follow the OSM wiki. In case of question, please ask me.
Thanks, Alex

hi sharmanubhav, please fix the problematic key, that you added yesterday to osm.org/node/5235300167
Thanks, Alex

Hi CartographerC, please follow the OSM wiki (wikipedia="language:Article" e.g. "en:Asia").
Thanks, Alex

Hi houtari, please follow the OSM wiki (wikipedia=lang:Article, not =http..), see osm.wiki/Key:wikipedia
Also adding wikidata is recommended.
Thanks, Alex

fixed typo tags, key="." x2

fixed typo tags

Hi vaggpit, I think you put a typo-tag ( "." = "yes") to way 625976944 + way 625982439.
Could you fix this please.
Thx, Alex